Wildlife Conservation in Farm Landscapes [1 ed.] 9781486303113, 9781486303106

Citation preview

WILDLIFE CONSERVATION IN FARM LANDSCAPES DAVID LINDENMAYER, DAMIAN MICHAEL, MASON CRANE, SACHIKO OKADA, DANIEL FLORANCE, PHILIP BARTON AND KAREN IKIN

D. LINDENMAYER, D. MICHAEL, M. CRANE, S. OKADA, D. FLORANCE, P. BARTON AND K. IKIN

Farming_wildlife_combo_Final_V3.indd 1

WILDLIFE CONSERVATION IN FARM LANDSCAPES

An increasing number of Australians want to be assured that the food and fibre being produced on this continent have been grown and harvested in an ecologically sustainable way. Ecologically sustainable farming conserves the array of species that are integral to key ecological processes such as pollination, seed dispersal, natural pest control and the decomposition of waste. Wildlife Conservation in Farm Landscapes communicates new scientific information about best practice ways to integrate conservation and agriculture in the temperate eucalypt woodland belt of eastern Australia. It is based on the large body of scientific literature in this field, as well as long-term studies at 790 permanent sites on over 290 farms extending throughout Victoria, New South Wales and south-east Queensland. Richly illustrated, with chapters on birds, mammals, reptiles, invertebrates and plants, this book illustrates how management interventions can promote nature conservation and what practices have the greatest benefit for biodiversity. Together the new insights in this book inform whole-of-farm planning.

14/04/2016 5:12 PM

WILDLIFE CONSERVATION IN FARM LANDSCAPES

Dedication For the many farmers with whom we have worked and are doing outstanding restoration and management on their farms For the Australian taxpayer – our sincere hope is that the investments that have been made in our work over the years have been more than repaid by an increased understanding of how to better manage our nation’s precious natural heritage and, at the same time, do productive and sustainable farming.

WILDLIFE CONSERVATION IN FARM LANDSCAPES DAVID LINDENMAYER, DAMIAN MICHAEL, MASON CRANE, SACHIKO OKADA, DANIEL FLORANCE, PHILIP BARTON AND KAREN IKIN

© David Lindenmayer, Damian Michael, Mason Crane, Sachiko Okada, Daniel Florance, Philip Barton and Karen Ikin 2016 All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO Publishing for all permission requests. National Library of Australia Cataloguing-inPublication entry Lindenmayer, David, author. Integrating wildlife conservation in farm landscapes / David Lindenmayer, Damian Michael, Mason Crane, Sachiko Okada, Daniel Florance, Philip Barton and Karen Ikin. 9781486303106 (paperback) 9781486303113 (epdf) 9781486303120 (epub) Includes bibliographical references and index. Wildlife conservation – Australia. Wildlife management – Australia. Agriculture – Environmental aspects – Australia. Farm management – Australia. Land use, Rural – Australia – Management. Michael, Damian, author. Crane, Mason, author. Okada, Sachiko, author. Florance, Daniel, author. Barton, Philip, author. Ikin, Karen, author. 639.90994 Published by CSIRO Publishing Locked Bag 10 Clayton South VIC 3169 Australia Telephone: +61 3 9545 8400 Email: [email protected] Website: www.publish.csiro.au This project has been assisted by the New South Wales Government through its Environmental Trust.

Front cover (clockwise from top left): tree plantings in farm landscape (Chris MacGregor), Eastern Grey Kangaroos (Dave Blair), Red Wattlebird (Jennie Stock), farm landscape (Dave Blair), Blue-banded Bee (Clement Tang), Southern Rainbow Skink (Damian Michael). Back cover: (left) Jacky Winters (Marlene Lyell), (right) Eastern Bearded Dragon (Chris MacGregor). Set in 11/13.5 Adobe Minion Pro and Helvetica Neue LT Std Edited by Peter Storer Editorial Services Cover design by Andrew Burns, Burns Creative Typeset by Desktop Concepts Pty Ltd, Melbourne Index by Indexicana Printed in China by 1010 Printing International Ltd CSIRO Publishing publishes and distributes scientific, technical and health science books, magazines and journals from Australia to a worldwide audience and conducts these activities autonomously from the research activities of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The views expressed in this publication are those of the author(s) and do not necessarily represent those of, and should not be attributed to, the publisher or CSIRO. The copyright owner shall not be liable for technical or other errors or omissions contained herein. The reader/user accepts all risks and responsibility for losses, damages, costs and other consequences resulting directly or indirectly from using this information. Original print edition: The paper this book is printed on is in accordance with the rules of the Forest Stewardship Council ®. The FSC® promotes environmentally responsible, socially beneficial and economically viable management of the world’s forests.

Contents

1

Preface

ix

Acknowledgements

x

Introduction

1

The underlying philosophy of our applied research work and the scientific process

3

The concept of ‘scale’

6

The structure of this book

2

8

Our use of common and scientific names

10

Caveats

11

Birds

13

Bird breeding success in woodland patches

14

Birds in nest boxes

16

Birds and paddock trees

18

Networks of species – friends and foes

19

Not all patches of bush are equal – bird responses to different kinds of broad vegetation structure

21

Why are there such marked differences in bird occurrence between the different kinds of vegetation?

25

Which attributes of remnants are important for birds?

26

Which attributes of plantings are important for birds?

27

Birds and travelling stock reserves

31

Pines and woodland patches

34

Bird responses to total vegetation cover at different scales

38

Bird occurrence over time

44

Do plantings get better with age?

47

Birds and the Millennium Drought

49

Management interventions and birds

51 v

vi

3

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Are birds good indicators?

54

Concluding comments

56

Mammals 57 Introduction 57

4

5

Habitat trees, paddock trees and arboreal marsupials – the case of the Squirrel Glider

59

Countryside elements and mammals – the special case of the Squirrel Glider

63

Mammals in nest boxes

65

What makes a good woodland remnant for arboreal marsupials?

67

Mammals and travelling stock reserves

68

Can there be too many mouths to feed?

69

Change in mammal abundance over time

72

Mammals in woodland patches surrounded by pine stands

74

Concluding comments

82

Reptiles 85 A way of categorising reptiles

87

Reptiles and regrowth woodland

92

Do reptiles use tree plantings?

97

Boulenger’s Skink and lizard morphology

104

Rocky outcrops and reptiles

106

Management interventions and reptiles

109

Reptile assemblages

110

Reptiles in woodlands surrounded by stands of pine

113

Concluding comments

115

Invertebrates 117 Kangaroos and beetles

6

120

Ants in grazing landscapes

121

Butterflies in grazing landscapes

123

‘Bugs’ and pines – what happens to invertebrates in eucalypt patches surrounded by pine plantations

129

Concluding comments

130

Vegetation cover and plants

131

Introduction 131 Increase in vegetation cover over time

131

Changes in vegetation attributes over time

135

How management interventions changes and improves vegetation

143

Contents

7

vii

Where in landscapes are key vegetation structures most likely to occur?

146

Paddock trees as keystone elements in agricultural landscapes – changes in paddock trees over time

148

Mistletoe as a key resource

149

Large logs as a critical resource

150

Home grown – native grass as a key habitat resource

150

Rocks are good for plants too

152

Regeneration dynamics in grazing landscapes

152

Where it is best to do plantings and how they should be designed?

153

Concluding comments

153

Managing wildlife friendly farms

155

Introduction 155

8

Protect what is already there

156

Restore what is missing

167

Putting it all together – evidence-based farm planning for integrating farming, biodiversity and other values

170

Developing evidence-based farm plans

176

Concluding comments

183

General discussion

185

Generating co-benefits – farming, carbon and wildlife

186

Being paid to conserve biodiversity on farms

189

The dangers of over-intensification

194

Fire and farm planning

194

Why monitoring is important

195

Concluding comments

196

Appendix 1 – List of common and scientific names

198

Appendix 2 – References

204

Index 212

This page intentionally left blank

‡7HQ&RPPLWPHQWVSSLQGG

$0

Preface

Our research team at The Australian National University (ANU) has worked for almost 17 years in Australian agricultural landscapes, especially in the temperate woodlands of southern New South Wales (NSW), but also more recently in mixed grazing and cropping areas in north-eastern Victoria, central western and northern NSW, and south-east Queensland. There is a large and rapidly growing body of research work from many people leading to many discoveries and important insights into wildlife management on farms. A lot of new findings have emerged in the past 5 years from numerous projects in Australia’s wheat/sheep belt. These findings have revealed that many things can be done to conserve wildlife while at the same time maintaining other key aspects of farm productivity and profitability. Although much new research has been published in the peer-reviewed scientific literature, we are acutely aware that very few people will ever know about these articles – let alone read them. It is important to communicate this information to a far broader audience than our scientific colleagues. Hence the writing of this short book. In a sense, we feel a sense of duty to communicate (in a hopefully readily understandable way) to the many farmers, catchment managers, revegetation practitioners and others with whom we have worked and we trust will find this book (and the science that underpins it) of practical use. We have written several past books on wildlife on farms and Australia’s extraordinary temperate woodlands, with CSIRO Publishing as our trusted publishing partner in those volumes. Our aim was not to repeat earlier information, nor to clumsily regurgitate the content of many dozens of scientific articles. Rather our objective was to report new findings that build significantly on our past work. In so doing, we hope to empower all of those people in rural Australia in their efforts to meet the significant (but not insurmountable) challenges of integrating conservation with ecologically sustainable agricultural production. The authors June 2015

ix

Acknowledgements

A large number of people and organisations have contributed to our research and management efforts in temperate woodlands and agricultural areas of southeastern Australia. A particular mention must be made of the hundreds of landholders who have allowed repeated access to their properties and in many cases done a lot of restoration and conservation work on their own land. Funding for our research has come from many sources including the Murray Local Land Services (especially supported through Emmo Willinck), Riverina Local Land Services (especially supported by Lilian Parker), North East and Goulburn Broken Catchment Management Authorities, Australian Research Council (Linkage Grants, Centre of Excellence), the Australian Government’s National Environmental Research Program, the Environmental Stewardship Program (via the former Lachlan Catchment Management Authority and especially David Trengove), the Long-term Ecological Research Network (LTERN), and the former Land and Water Australia. We thank the many scientific colleagues and friends with whom we have worked and published on farm and woodland conservation over the years including (among many others) Rebecca Montague-Drake, Richard Hobbs, Suzanne Prober, Andrew Bennett, Alan Welsh and Christine Donnelly. No book writes itself and we thank Tabitha Boyer and Claire Shepherd for assistance with many aspects of book production. We also thank Clive Hilliker for his assistance with scientific illustrations. We would also like to thank the many talented photographers who provided their work to make this book so visually engaging. John Manger and Tracey Millen from CSIRO Publishing have been wonderful with their support in publishing syntheses of our work over many years. Their efforts are most gratefully acknowledged.

x

1 Introduction

An increasing number of Australians want to be assured that the food and fibre being produced on this continent has been grown and harvested in an ecologically sustainable way. This will increasingly be a major challenge for society as human populations continue to expand, rates of resource consumption increase, and some kinds of resources become increasingly difficult to grow, find or extract. The challenge is: •

How can we maintain or even increase food production without undermining the productive capability of farms and without significantly eroding biodiversity?

Ecologically sustainable farming means producing food (including meat) while at the same time maintaining the quality of soils, preserving (and even expanding) patches of native vegetation, and conserving the array of species that are integral to key ecological processes such as pollination, seed dispersal, natural pest control and the decomposition of wastes (e.g. the carcases of dead animals). The challenge of developing ecologically sustainable farming management practices has been a major objective of research by The Australian National University (ANU) in agricultural south-eastern Australia since the late 1990s. Our work has grown over the past 17 years to encompass sites and farms from central Victoria, through NSW to south-eastern Queensland. In all, we now work on over 847 field sites that are located on over 300 farms (Table 1.1; Fig. 1.1). Indeed, our research – part of which entails many repeated visits to permanently established field

Nanangroe Property, South West Slopes Bioregion, New South Wales

South West Slopes Bioregion, New South Wales

Murray catchment, New South Wales

North East and Goulburn Broken catchments, Victoria

Box Gum Grassy Woodland EVC between Henty (NSW) and Warwick (Qld).

South West Slopes Restoration Study

Woodland Intervention Study

Victorian Biodiversity Monitoring Program

Environmental Stewardship Program

Study area – location

Nanangroe Natural Experiment

Monitoring program

2010

2010

2007

2001

1998

Year of establishment

325

40

111

218

143

Number of sites

Threatened EVC on private property.

Two threatened EVCs on private property, Crown land roadside reserves, Trust for Nature covenants and state parks

Four threatened woodland EVCs on private property and travelling stock reserves

Several woodland EVCs on private property, tree plantings, Crown land roadside reserves and travelling stock reserves

Several woodland EVCs on private property and NSW State Forest remnants and pine plantations

Experimental design

The information reported in this book is based on surveys conducted across various ecological vegetation communities (EVCs) in each study area.

To compare spatial and temporal patterns of woodland biodiversity between remnants placed under an environmental stewardship agreement and remnants managed for primary production.

To compare spatial and temporal patterns of woodland biodiversity between remnants under different management regimes in two different vegetation types.

To compare spatial and temporal patterns of woodland biodiversity between remnants under different management regimes in four different vegetation types.

To compare spatial and temporal patterns of woodland biodiversity between tree plantings of various size and shape and remnants of different growth forms.

To compare spatial and temporal patterns of woodland biodiversity between remnants surrounded by pine plantations and remnants surrounded by grazing land.

Overarching aim of the research

Table 1.1.  Long-term biodiversity monitoring programs being conducted by the Fenner School of Environment and Society at the ANU in the temperate woodlands of south-eastern Australia and which form the basis of work summarised in this book.

2 W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

1 – Introduction

3

Fig. 1.1.  Map of the location of field studies and site locations conducted by the ANU throughout the agricultural areas of eastern Australia.

sites – is arguably one of the largest scaled terrestrial monitoring programs in the world. Visiting so many sites, farmed in different ways and in different regions, has provided a large number of the insights that feature throughout this book. On this basis, we outline ways that different groups of animals and plants might be conserved on farms, while at the same time ensuring that those farms are viable businesses.

The underlying philosophy of our applied research work and the scientific process Our underlying research philosophy is to provide high-quality scientific information to landholders, regional land managers and other interested people to help them

4

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Positive conservation management is often billed as a negative for farm economics. Not so. On this farm near Wagga, the Chalkers have worked hard to improve the quality of the waterbodies by strategic fencing and controlled stock access points around dams and creeks. This has led to improved water quality for stock and assisted in maintaining water availability during prolonged dry periods. At the same time, waterbody management has significantly improved bird biodiversity on the farm, with a dramatic increase in bird species richness (particularly of bird species of conservation concern) over the past decade. Photo by Mason Crane.

implement best practice farm conservation and farm management. That is, we gather the scientific evidence to guide making decisions such as where and when to do plantings or which remnants of native vegetation are the best ones to protect. There are several ways in which robust scientific evidence can be gathered. The approach used by our team at the ANU is relatively simple to write down, but painstaking and time-consuming to do. We outline this approach below as we believe that it is important for readers to appreciate how the science is conducted and how our conclusions are reached: 1 A land manager or member of our scientific team identifies a significant problem or set of issues for which there is currently no definitive scientific answer. 2 A field study is rigorously designed to address the problem. This is typically in a collaboration between scientists, professional statisticians and land managers (including farmers). This part of the work usually entails carefully defining the

1 – Introduction

3 4 5 6

7

8

9

5

questions to be posed, the statistical design that can be used to implement a study to answer those questions, and the methods employed to collect the data in the field. A small pilot study may be conducted to determine if the experimental design proposed to implement a study is actually possible to do on the ground. The results of the pilot study are examined and the study (if viable) is then fully established. Following initial establishment, our field studies may run for several years and sometimes decades. At various intervals during long-term data collection, a sixth (and critical) stage is that information from the field is subjected to detailed statistical analysis. This is typically done through a partnership between an expert statistical scientist and one or more ecologists. The results of statistical analyses are written up and then assessed by colleagues within the Fenner School at the ANU. Scientific articles demand precise writing to emphasise what discoveries have been made. It is also essential to make it clear what scientific and statistical methods have been used so that other scientists could replicate the work if they so desired. When the scientific article is of sufficient quality and all the details of the analysis and writing are finalised following comments from colleagues, it is submitted to a national or international scientific journal to be considered for publication. Such articles typically undergo thorough critique from anonymous referees, with requests to revise the article to improve its quality. This eighth stage is a very tough one in which a scientific paper is often rejected by one or more journals. The article must then be further revised and improved before it is submitted to another journal. It may take submission to four or five journals before a scientific article is finally accepted – a process that may take 2–3 years if the target is a high-quality international journal. This long and arduous process of science publishing requires considerable patience, a thick skin (to deal with repeated criticism and rejection), and a massive dose of persistence. Many members of the public are unaware of just how tough (but also rigorous) the scientific publishing exercise can be. Widely communicate the scientific findings to a broad audience. When a scientific article is published, it is then available for other scientists, as well as any member of the public or management organizations, to read. However, few people even know that most of scientific journals even exist, let alone read the highly technical articles they contain. We therefore work hard to produce books (such as this one), posters, glossy brochures, calendars and DVDs. We also present our findings to natural resource managers in workshops, to landholders at field days, and give lectures to school groups. These activities are designed to ensure that our new scientific findings are communicated and accessible to a wide audience beyond scientists and academics.

6

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Repeated and careful measurements of biodiversity made over many years provide the essential, high-quality empirical data needed to determine how species are changing, and why they are changing. Many members of the research team at the ANU have been working on the same sets of farms in Victoria, NSW and south-eastern Queensland for well over a decade. Photos by Damian Michael, Dan Florance, Mason Crane, Dave Blair and Thea O’Loughlin.

Of course, there are many different approaches to creating quality evidencebased science beyond those underpinned by the collection of field-based empirical data. These include genetic analyses of samples collected in the field, systematic reviews of the literature, and simulation modelling (such as predicting the viability of populations of animals or plants). We have employed all of these methods in our 17+ years of research in Australian agricultural landscapes. But our general approach is always the same. That is, rigorously gather scientific information, subject those data to the best possible statistical analyses, write up the results at the highest possible standard, and widely communicate key findings.

The concept of ‘scale’ Our many studies have been conducted at different spatial scales – from a single bird nest or large hollow tree through to entire regions or even multiple regions. As an example, we have worked on the success of individual nests of birds, the use of

1 – Introduction

7

individual trees (such as paddock trees) by marsupial gliding possums, on the importance of particular patches (e.g. a planting or a woodland remnant) for birds, reptiles and mammals, and on the value of entire farms and landscapes for supporting populations of particular species and assemblages of animals. These different studies completed at different spatial scales provide different insights about animal responses to agricultural environments and what management actions might be most effective at particular scales. Indeed, exciting discoveries can be made when our datasets are simultaneously analysed at several scales.1 These multi-scaled studies tell us that actions at one scale (such as the farm level) can have profound effects on biodiversity at other scales, such as the likelihood a given patch will be occupied by a particular species of bird (see Chapter 2). Such investigations also indicate that actions at a given scale, such as the decision to establish a planting or fence a woodland remnant, can (and does) make a positive difference to the environment at several scales.

Improving outcomes for biodiversity on farms requires a strong working partnership between landholders and researchers. Farmers implement particular kinds of management interventions on farms and researchers design rigorous scientific studies to determine the effectiveness of these interventions for improving outcomes for wildlife on farms. Scientists then communicate their results to farmers and suggest ways in which management might continue to be improved (e.g. by changing the width and shape of plantings). Updated management actions then continue to be subject to research and monitoring, underscoring the value of farmers and scientists working together to improve the integration of wildlife conservation and agricultural production. Photo by Mason Crane.

8

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Another kind of scale is time. The scientific jargon sometimes used is ‘temporal scale’. Environments are never static and Australia, in particular, is famous for climatic variability: all landholders are critically aware of the major changes in the environment between very wet and extremely dry years. It is therefore very important to track and quantify changes in the environment and in populations of plants and animals over time. Documenting the effects of time is crucial for other practical reasons. Long-term work is needed to answer vital questions such as: How soon after planting will an area be colonised by birds or possums? Will an area naturally regenerate if it is fenced off? Yet, precious few ecological studies in Australia are conducted for more than a handful of years at best. We have worked extremely hard to break that unfortunate tradition and many of the insights we summarise in this book are based on many years of continuous detailed field research. Sometimes long-term studies lead to new perspectives that appear to be inconsistent with previous work – including our own previous studies. For example, our early work suggested that plantings rarely supported any species of possums or gliders.2 However, new studies completed over a longer period indicate that species such as the Common Ringtail Possum are increasingly using replanted areas. This highlights the value of continuing to complete measurements at many field sites over many years.

The structure of this book This book comprises a series of short chapters that attempt to summarise our key research findings in simple, succinct language. Each of the following chapters focuses on a particular group of organisms – birds (Chapter 2), mammals (Chapter 3), reptiles (Chapter 4), invertebrates (Chapter 5) and plants (Chapter 6). Our final chapter is a general overview and synthesis of key principles and practices on farms and in farming landscapes, with some limited commentary on future challenges, important knowledge gaps that we must strive to close, and ideas on ecologically sustainable farming (see Chapter 7). Integrating conservation and agricultural production does not mean driving farmers off their land, nor does it entail conservation action on every hectare of a farm. This would be totally impractical, nonsensical and unnecessary. Rather, the marriage of conservation and farming requires making informed decisions (guided by good scientific evidence) about where particular management interventions (such as fencing or replanting) will be most cost effective and most ecologically effective. This is the science of whole farm planning – a topic that features heavily in Chapter 7. We have deliberately kept each of our chapters as short as possible and to the point. The information we present is a highly summarised version of detailed research that can be found in much longer and often more densely written peer-reviewed scientific articles. In many places in the book, we provide information that is referenced with a citation to a particular study (as an author

1 – Introduction

9

Many farms look much like the ones in these two images. They have been highly modified through extensive clearing and conversion to exotic pastures dominated by just a few annual grasses (e.g. the top image). These highly simplified landscapes provide limited or no habitat for most of species that would have formerly occurred in these areas. These landscapes are, however, not without hope in terms of opportunities for restoration. As discussed throughout this book, there is an increasing body of science to guide management actions that improve outcomes for biodiversity while at the same time maintaining (and often improving) farm productivity. These actions include better protecting existing remnant woodland and paddock trees, encouraging natural regeneration of woodlands, as well as strategic replanting. Photos by Dave Blair.

10

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

and date), which is then listed in Appendix 2 at the end of this volume. Readers are more than welcome to contact us if they want access to seek further information on a given topic. We are happy to send out our papers, brochures and other materials, especially as we recognise that some scientific articles are either very difficult to obtain, expensive to buy, or even totally unavailable to the general public. The seven chapters in this book vary significantly in length. This is for good reason. Some groups, particularly birds, have been researched far more deeply than others. There is much more research to summarise about them than, for example, mammals and especially invertebrates, because these have only recently become a focus of our increasing study effort. Because some groups of animals share requirements for similar kinds of resources, there has inevitably been some repetition in material between chapters. For example, tree hollows and mistletoe are resources used by both birds and mammals. Similarly, tussock grasses are important habitats for reptiles and invertebrates. While we have endeavoured to limit repetition, some overlap of material was necessary to provide a comparatively complete story on the new scientific findings that have been emerging for a given group. Each chapter includes many photographs and a small number of figures and graphs. The photos, in particular, are often accompanied by a relatively long caption that describes either important additional information or provides interesting facts about a particular plant, animal or place. There are several other features that characterise the text of many of the chapters. First, we have included several short boxes that briefly explore additional issues that we felt might be of general interest to readers. Some of these are linked to issues associated with farm management. Others outline interesting insights into the habitat requirements, or other aspects of the ecology of animals or plants or animals that might occur on some farms. Second, we provide a short description on how particular groups of animals or plants are studied and how scientific data on them are collected. Third, most chapters discuss implications of our work for farm management. This is because the era of writing scientific articles for the sheer sake of it should be well and truly over. Rather, one of our aims is to carefully consider the practical application of our work for how farms might be managed in ways that ensure the maintenance of productive and viable grazing and/or cropping enterprises while at the same time taking steps to ensure the conservation of native plants and animals.

Our use of common and scientific names We use the common names of animals and plants throughout this book. But the same common name is sometimes used for several quite different species. Conversely, the same species can sometimes have more than one common name.

1 – Introduction

11

A note on royalties and ‘profits’ Some people ask us what happens to ‘all the money we make from our books’. The sad reality in Australia is that precious few authors make much money from books – even famous novelists. We are not among the high rollers. Indeed, our aim is not to make money, but rather widely communicate our scientific findings. Nevertheless, the money generated from this book (and many others we have written) goes into a fund that is used to support student and other projects, thereby re-investing in gathering the knowledge to continuously improve efforts to maintain Australia’s natural heritage.

However, no two species have the same scientific name. We therefore provide a detailed list of the common names and scientific names of all the plants and animals mentioned in this book (see Appendix 1).

Caveats We have worked for a comparatively long time on many aspects of on-farm conservation and management – as we hope readers will appreciate from the content of the chapters that follow. However, we are acutely aware there are many topics on which we have not worked. For example, we have conducted only limited work on aquatic ecosystems, although a few of our early studies were on frogs on farm dams3–5 (see Box on p. 12). We have not studied other aquatic animals (including fish and invertebrates), nor the plants in these aquatic ecosystems. We also have not completed studies of microbats and flying foxes (also called fruit bats). This is, in part, because the large-scale movements of these species (often over tens of kilometres in a single night) make it difficult to quantify their habitat and spatial landscape requirements. Another area we have not examined is the biodiversity of soil environments, including the links between soil microfauna (such as earthworms), soil productivity and paddock fertility. Finally, we readily acknowledge that much of our work focuses on mixed farms in what has been loosely dubbed the ‘wheat/sheep’ belt, although many of our farms also graze cattle and grow crops (such as oats, barley, canola and rice) other than (or in addition to) wheat. Our work does not therefore encompass broad-scale cropping enterprises such as what might be seen in inland irrigated rice and cotton farms or the massive wheat cropping farms of Western Australia. Integrating agricultural production and environmental values on those kinds of broadacre cropping farms is beyond the scope of our research. Additional work is needed to best guide what should be done in those kinds of places.

12

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Repeated measurements at long-term sites is by far the best way to gain a deep understanding of how biodiversity responds to improved farm management. Our team at the ANU has nearly 900 such long-term sites and marked changes in the amount and structure of the vegetation have been documented on many of these sites over the past 10–15 years, largely as a result of good management such as grazing control, pest animal control, reduced levels of firewood harvesting and weed control. At the same time, many species of birds have responded positively to changed management. Photos by Damian Michael.

The information in this book is focused almost entirely on results drawn from our own research at the ANU. This is, in part, because it is work with which we are most familiar and best understand. We therefore have not dedicated much text to the (often excellent) work done by others actively working on biodiversity and environmental management in agricultural ecosystems. We are well aware of much of that work but do not feel we are qualified (nor do we feel that it is appropriate) for us to summarise that research here. We apologise to our colleagues who take exception to our approach.

The Chalker’s Farm and aquatic ecosystem integrity – better for stock, better for wildlife Although we have done comparatively little recent formal scientific work on managing farm dams, rivers and other ‘wet bits’ on farms, some of the farms on which we work have been greatly improved as a result of careful management. The Chalker’s farm near Wagga is a great example, as is Bellingham’s property close to Tarcutta, both in southern NSW. In both places, the dams and streamlines have been fenced off and stock access points have been constructed. This has allowed streamside (also known as riparian) vegetation to recover, leading to a dramatic improvement in water quality. This, in turn, leads to better stock health and higher stock prices at market. We have documented significant increases in populations of birds and other animals on these farms over the past decade – a win for the farmer and a win for the environment.

2 Birds

Birds are not only the most visible group, but also the most diverse group of vertebrates on farms. The 170+ species we have recorded in our surveys over the past 17 years is about double the number of species of reptiles – the next most species-rich group. Birds play many key ecological roles in farming landscapes, ranging from pest control and pollination, through to seed dispersal. The birds on farms range markedly in size and diet. For example, they include tiny seed-eating birds such as the Diamond Firetail (17 g) and ‘micro-predators’ such the Weebill (Australia’s smallest bird at only 6 g, which glean insects from eucalypt leaves) through to large omnivores such as the Brolga (6.5 kg) and imposing predators such as the Wedge-tailed Eagle (4 kg). Our work on birds on farms has encompassed a wide variety of studies – from the success of individual nests and use of individual nest boxes, the value of individual paddock trees, the use of remnant woodland patches and colonisation of plantings, through to the characteristics of entire farms (and even landscapes) that make them suitable for use by particular species of birds. In this chapter, we briefly summarise some of the key findings of our work on birds by describing findings at different scales – from individual nests through to entire landscapes. We then describe how populations of birds have been changing over the past decade or more, including during the Millennium Drought in the 2000s. The concluding section in this chapter outlines some of the important implications of our work for farm management and its integration with the environment.

14

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

How are birds studied in agricultural landscapes? There are many different methods that can be used to study birds in the field. The one used by the research team at the ANU is called the ‘point interval count’ method. It entails an observer recording the numbers of all species of birds that are seen or heard within a set period (in our case 5 min) and set distances (in our case 0–25, 25–50, 50–100 and > 100 m) from a permanent marker point. We have established marker points at the 0 m, 100 m and 200 m positions along a marked transect on each of our 847 long-term research and monitoring sites in agricultural areas from central Victoria to south-eastern Queensland. Additional rules are used to ensure the quality of the field data gathered on birds is as high as possible. These include: (1) Bird surveys are undertaken at the same time (in winter and spring) in any given year. (2) Bird surveys are completed only during good weather. (3) Only highly experienced observers (with more than 10 years field experience) conduct surveys of birds. (4) All sites are surveyed at least twice in a given survey period. The second survey is completed by a different observer from the one who completed the first survey. The second survey is also conducted on a different day. This approach reduces observer and day effects on the data. (5) Data gathered by the different observers are carefully assessed on a regular basis by a statistician to ensure its quality, with non-performing observers dropped from the field survey team.6 Counting birds takes considerable skill and has many of the hallmarks of learning a language. During formal survey periods, most birds are ‘heard but not seen’. Many species have several different calls and sometimes males and females will use different calls. There may also be dialects, with the same species using a slightly different call in different parts of its distribution (the Crested Shrike-tit is one example). In addition, some species such as the Brown Thornbill and the introduced Common Starling are accomplished mimics of other birds. These complexities mean that considerable mental agility is required by the observer to avoid misidentification.

Bird breeding success in woodland patches Most of our studies of birds in agricultural landscapes have been those that have documented the presence and/or abundance of bird species in patches of woodland or in plantings. Most of the following sections are based on that kind of field information. However, the occurrence of a species in a particular patch might not tell us very much about whether that species is able to breed successfully and hence whether populations are likely to persist in the medium to long term. There are many key questions about bird breeding success in agricultural landscapes. These include: • •

Is bird breeding success affected by the size or other characteristics of a patch? Is there are difference in bird breeding success between broad kinds of vegetation such as plantings and woodland remnants?

2 – Birds

15

The Crested Shrike-tit is one of the more intriguing birds found in temperate eucalypt woodlands. The species also inhabits dry forests and even tall wet eucalypt forests such as the spectacular Mountain Ash forests of Victoria. One of the advantages of the ANU team working in many different environments is recognition of differences between individuals of the same species living in various ecosystems. For example, the calls of the Crested Shrike-tit in temperate woodlands are quite different from birds inhabiting wet forests. The Crested Shrike-tit is closely associated with eucalypt tree species that develop hanging bark streamers around the trunk and large lateral branches. Clumps of bark provide important aerial microhabitats for a suite of invertebrates, including tree crickets, spiders and other small animals. These animals are, in turn, prey for the insectivorous Crested Shrike-tit, which uses its razor sharp bill to tear open bark streamers in search of prey. Bark searching by the Crested Shrike-tit is anything but subtle; in fact this activity can be so noisy that the presence of these birds is given away well before the bird itself can be seen. However, the sounds of foraging by the Crested Shrike-tit are increasing uncommon in the temperate woodlands of south-eastern NSW, as the species has declined substantially over the past decade. Photo by Alwyn Simple.

We sought to answer these questions in an intensive study in southern NSW in which the number of nests in 24 plantings and 8 woodland remnants was counted and breeding success was documented.7 The work produced several important findings. First, we uncovered strong evidence of reduced breeding success in linear woodland remnants and strip-shaped plantings. Second, breeding success was significantly higher in larger patches, and this effect was strongest for species of conservation concern such as Jacky Winter, Crested Shrike-Tit, Brown Treecreeper and White-browed Woodswallow. Third, although birds attempted to breed irrespective of the size of the patch in which they were living, those that were most successful were in larger patches. This suggests there was a higher loss of eggs and nestlings in smaller patches. A second study is comparing bird breeding success between woodland remnants on farms and woodland remnants surrounded by maturing stands of

16

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Weebill is one of the bird species that has been increasing in the temperate woodlands of south-eastern NSW over the past 10–15 years. It is Australia’s smallest bird and responds strongly to the dense vegetation structure created in plantings, especially block-shaped plantings. Although the Weebill is tiny, it makes a loud and strident call that almost seems to announce its identity; sounding literally like ‘I am a Weebill, I am a Weebill’. Photo by Ian Bool.

pine plantation trees. This work is still in its preliminary phase, but already there is compelling evidence that more birds attempt to breed and nest more successfully in farmland remnants than woodland remnants in plantations. Moreover, although a wide range of species attempted to breed on farms, only large predators such as the Australian Raven and the Australian Magpie successfully reproduced in the remnants surrounded by Radiata Pine plantations. The follow-up stage of this exciting new work has entailed deploying artificial nests in woodland remnants and filming them with remote infrared cameras to determine which nests are successful and, for those that are not, which species are eating the eggs in the artificial nests. This work has revealed that the primary predator causing nest failure was, perhaps unexpectedly, the Australian Magpie.

Birds in nest boxes Australia supports a disproportionately large number of species that are dependent on cavities or hollows in large old trees. However, large old trees are rapidly being lost from many agricultural landscapes around the world, including those in

2 – Birds

17

eastern Australia.8,9 This is occurring for a wide range of reasons including intense grazing (which prevents tree regeneration) and fire, which often consumes large old trees. One of the strategies often advocated by managers to counter the loss of large old trees is to install nest boxes as a source of artificial cavities. We have been conducting a 3-year study of nest box effectiveness for hollow-dependent animals in a range of regions on the South West Slopes of NSW. The study involves monitoring over 330 nest boxes characterised by a wide range of sizes, shapes and entrance types – all of which strongly influence which species use them.10–12 The majority of the nest boxes were erected as an offset for the loss of large old trees following the upgrade of the Hume Highway duplication project. About half of the nest boxes show signs of having been occupied by any animal, with ~3–4% of boxes in any given year being used by birds. A total of eight species of birds has been recorded using the nest boxes to date. The majority are common and widespread species such as the Eastern Rosella and the Galah. The Brown Treecreeper is the only species of conservation concern that we have recorded using the nest boxes, but detections of it were limited to one individual in one year (2010). Unfortunately, the bird species with the highest rate of occupancy is the exotic pest, the Common Starling.

Sometimes called by the name Leatherhead (because of dark featherless skin on its head), the Noisy Friarbird has many characteristics that are typical of Australian honeyeaters: it is large, aggressive and highly vocal. The Noisy Friarbird is also nomadic and partially migratory, moving large distances to find nectar, pollen and insects. Photo by Greg McLachlan.

18

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Ornithologists have long understood that Australia is home to many large and aggressive honeyeaters. The Red Wattlebird is no exception. Our long-term field survey data show that numbers of the Red Wattlebird have been increasing significantly over the past 15 years, especially in plantings. The Red Wattlebird is widely thought to be aggressive, but our data on interactions between the species have shown that this is not necessarily the case in the many areas of temperate woodland that we have studied. Studies elsewhere in Australia (such as in South Australia) have suggested that the Red Wattlebird is particularly aggressive towards other bird species when nectar and other resources are limited. However, even during the prolonged drought conditions during the 2000s, our data did not contain evidence of such negative interactions between the Red Wattlebird and other honeyeater species (or any other woodland birds). It is possible that the patchy and dispersed patches of woodland mean that it is difficult for individual birds to actively and aggressively defend food resources against other birds. Photo by Jennie Stock.

The results of the nest box program to date have been somewhat underwhelming across all years since monitoring commenced. High rates of attrition of the boxes (in the two years from 2010 – 2012 almost 10% of nest boxes checked by our group had failed) reflect poor construction and especially inappropriate attachment to trees. These problems have contributed to high rates of nest box failure, which are further compounded by the relatively high rates of occupancy by feral honeybees, which can actively compete with vertebrates for hollows.

Birds and paddock trees Paddock trees have often been called ‘keystone structures’. This is because they play disproportionately important (keystone) roles in agricultural landscapes, not only for biodiversity but also in other ways such as producing abundant flowers (which is important for honey production) and storing large amounts of carbon.

2 – Birds

19

The Eastern Yellow Robin is a spectacular bird that is most often found in the darkest and most sheltered parts of woodland patches. This species is now rare in woodlands and largely confined to very large patches subject to limited grazing pressure. Places where the Eastern Yellow Robin occur also tend to support high numbers of other woodland bird species, including a range of species of conservation concern. Photo by Greg Miles.

Our research has shown that paddock trees also provide stepping stones that assist woodland birds move through agricultural landscapes.13,14 For example, species such as the Red Wattlebird and Noisy Friarbird preferentially use paddock trees during their movements through farming landscapes, rather than fly over open paddocks. We have completed other important work on paddock trees. For example, we have found that plantings established around paddock trees support more species of native birds than plantings without these large old trees.15 In addition, birds of conservation concern are more likely to occupy those patches of remnant woodland that are surrounded by scattered paddock trees than in patches where such important keystone structures are rare or absent in the surrounding landscapes (see below).16

Networks of species – friends and foes The famous cliché ‘no man is an island’ applies not only to people but equally to many other organisms. There are many kinds of inter-relationships between species that lead to interesting patterns of dependence and co-occurrence. Some species are predators or parasites and cannot survive without their prey or hosts.

20

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Nest boxes are widely used as a replacement for natural hollows in planted woodlands. This is because large old hollow-bearing trees that provide critical nesting sites for many species are typically absent from plantings. Only a subset of hollow-dependent animals use nest boxes. One of these species is the Eastern Rosella. However, the Eastern Rosella only uses nest box in plantings where the Common Brushtail Possum is absent. This is perhaps because the Eastern Rosella (and its eggs) is prey for this large and widespread native mammal. Photo by Giovanni M Cordeiro.

For example, there are many species of parasitic cuckoos in Australia and populations of them would not survive without being able to lay their eggs in the nests of host birds. Examples from agricultural areas are the Pallid Cuckoo and Horsfield’s Bronze Cuckoo. Other species can be aggressive and chase away other possible competitors. The hyper-aggressive Noisy Miner is infamous for doing this and suppressing populations of smaller birds.17 Other honeyeaters such as the Red

2 – Birds

21

Wattlebird, Noisy Friarbird and White-plumed Honeyeater are also known to be ‘grumpy’ towards other birds. We have completed a detailed examination of the structure of bird communities in woodland remnants and plantings located in grazing and cropping landscapes in south-eastern NSW. The work is based on bird data gathered in more than 120 patches over 12 years. A novel method of statistical analysis – network association analysis – was developed specifically to explore which species typically co-occur with others and whether there are positive or negative associations between particular pairs of species.18 Network association analysis produces spectacular diagrams highlighting the prevalence of interactions between species and these differed markedly between woodland remnants and plantings (see Fig. 2.1). There are large differences between which species associate (either positively or negatively) between woodland remnants and plantings. The work indicates that, for example, species such as the Whiteplumed Honeyeater are typically associated with a large number of other species. This is contrary to what some people thought likely for this seemingly aggressive native bird. Conversely, many species avoided sites that supported the Noisy Miner, a result entirely consistent with what has been widely observed and documented for this despotic bird.19 However, there were several birds that had even stronger negative associations with other species. Prominent examples were the Grey Butcherbird and the Pied Butcherbird. The reasons for this unexpected result are presently not clear but they may be associated with the fact that the Grey and Pied Butcherbirds are predators and well known for taking eggs, nestlings and fledglings of other bird species. They also are known to prey on adults of small birds.

Not all patches of bush are equal – bird responses to different kinds of broad vegetation structure Many grazing and cropping farms support quite different kinds of native vegetation structure – some areas of old growth woodland, patches of woodland regenerating after fire, thinning or reduced grazing pressure, and restored areas following deliberate replanting (see Fig. 2.2). Humans can readily recognise these areas as distinctly different kinds of vegetation – some are open with large trees, others support multiple stems and others form thickets of dense vegetation. A key question then is: •

How do birds also respond to these different kinds of vegetation?

To answer this, we compared birds found in old growth woodland, woodland regenerating after physical disturbance to the tree from fire or fire wood collection (also known as epicormic or coppice regrowth), regrowth woodland re-established from seedlings after the intensity of livestock grazing has been reduced (seedling

22

hrik o-s

n

cko

ep

er

Cu

cre

ed

Br

at ie l

ow

nT ree

-fac

gpie

Rave alian

Bla ck

Austr

d Thornbill

Australian Ma

Yellow-rumpe

gtail

r

llo

allo

gh

Co ck

wa

Sw

rille dT

Supurb

ds

ou

erb

oo

r te ea

Sup

Ch

me

ed

lco

W

ing

ed

y ne Ho

ow

We

e-w

br

nge -wi

hit

e-

Wa Willie

ite Wh

W

hit

ed m lu -p te hi

W

W

e

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Br

on

m

m

Co

w

S on

mm

Co

w

st Cre

rot

Crested

Striated Pardalote

Dusky

er

Eas

tler

tern

Whis

So

ey

it

Shrike-t

bi

ot

tle

urra

ove eful D

Noisy Miner

kab

Peac

utc dB

d

Koo

bird

Pie

bir

sh

er

her

dP

ella

ru

pe

Ros

th

bird

arr

at W

wallow

e-

int

um

Woods

rik

yW

ng

d-r

er

Sh

ck

ghi

Friar

Re

tch

y

Ja Lau

Little

Magpie-lark

Re

Bu

re

rd

sF

G

a lyc

lah

Gr

er

tch

s tle

s Re

Ga

rk

la ng

d

s

fou

Ru

n

Crimson Rosella

Kingfish ous

igeo

ed P

Par

ren

Ruf

ling

tar

Fairy-w

Sacred

ing

ew

z on

Key to species associations Strong positive Positive Negative Strong negative Very strong negative

Fig. 2.1.  Network diagram showing the strength of the association (i.e. degree of spatial overlap) between pairs of bird species in woodland patches in the South West Slopes. Species with positive associations are more likely to occur together than we would expect by chance, while negatively associated species are unlikely to co-occur. Redrawn from Fig. 1 of Lane and colleagues (2014).18

regrowth), and replanted woodland resulting from tree plantings programs. Of course, no two patches of vegetation are exactly the same – each one is different in its own unique way, even if such differences seem to be quite subtle. That is, each patch is different from any other in terms of location (e.g. gully, midslope or ridge), history of past disturbance, or adjacency to other kinds of vegetation. We know

2 – Birds

23

Fig. 2.2.  Montage showing four different structural kinds of vegetation. Photos by Damian Michael, Dave Blair and David Lindenmayer.

that these differences can matter for biodiversity (including birds), so how do we solve these problems in a scientific way? The answer is to have many different replicates of the same broad kind of vegetation and then look carefully for general differences between the broad groups of sites. To do this, we have statistically quantified the differences in the bird assemblages inhabiting 193 patches of vegetation on farms that have been rigorously surveyed for birds every 1–2 years for well over a decade. These 193 patches are comprised of 63 plantings, 71 old growth woodland patches, 27 epicormic regrowth woodland sites and 32 seedling regrowth woodland sites.20 This painstaking work has shown that markedly different bird assemblages occur in the broad kinds of vegetation structural forms found on a farm. Of the 178 individual species of birds that we recorded during the 10 years of work, 29 species occurred significantly more often in tree plantings, 25 significantly more often in seedling regrowth, 20 significantly more often in epicormic regrowth, and 15 significantly more often in old growth. We found that many bird species of conservation concern were more often recorded in epicormic regrowth, seedling regrowth or plantings. In contrast, no species of conservation concern were

24

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

recorded more than expected in old growth. For example, the Grey-crowned Babbler and White-browed Babbler were significantly more likely to occur in seedling regrowth than other growth types. The Black-chinned Honeyeater was most often found in seedling regrowth and epicormic regrowth. The Hooded Robin was more likely to occur in epicormic regrowth and particularly plantings than other growth types. The Brown Treecreeper, Crested Shrike-tit, Dusky Woodswallow and Jacky Winter were least likely to be recorded in plantings and most likely to be recorded in epicormic regrowth and seedling regrowth. Birds of conservation concern most often recorded in plantings included the Red-capped Robin, Rufous Whistler, Speckled Warbler and Flame Robin. However, a suite of hollow-dependent bird species such as the Galah, Sulphur-crested Cockatoo, Eastern Rosella and Laughing Kookaburra were more likely to be found in old growth woodland, perhaps because the abundance of hollow-bearing trees was greatest in these places.20

The Common Starling is a widely despised pest bird in Australia that was brought to the continent by Europeans. It is one of the bird species mentioned in the famous plays by William Shakespeare. A goal of members of acclimatisation societies was to establish all of Shakespeare’s birds in England’s colonies. Like many exotic species, it required many attempts to successfully establish populations of the Common Starling in Australia. Unfortunately, it is now widely established in many parts of rural (and urban) Australia. Our recent data suggest that populations of the Common Starling declined significantly during the drought of 2000s, although they appear to have rebounded following recent wetter periods. The Common Starling nests in tree hollows and is likely to compete with other cavity-dependent native birds. However, its nesting behaviour is highly flexible and the species is also is able to construct nests in buildings and other human infrastructure. The Common Starling makes a wide range of calls, but is also able to mimic the songs of other birds. Photo by Greg McLachlan.

2 – Birds

25

The Yellow-faced Honeyeater is a highly mobile, migratory bird species. Our long-term studies have indicated that it is strongly associated with exotic Radiata Pine plantations from which it ‘spills over’ and colonises adjacent patches of remnant woodland. The Yellow-faced Honeyeater is so successful in occupying plantation-dominated ecosystems that it has displaced other species of honeyeaters that were formerly widespread and abundant such as the White-plumed Honeyeater. Photo by Greg Miles.

Why are there such marked differences in bird occurrence between the different kinds of vegetation? We suggest that the differences are most likely to be a result of growth-type differences in the structure of the vegetation such as stem density and the prevalence of tree hollows and logs. For example, large numbers of stems in plantings and seedling regrowth may explain the prevalence of small bird species such as the Speckled Warbler and the Eastern Yellow Robin (which are of conservation concern) that forage in and around these densely stocked areas. However, a range of factors are likely to influence the occurrence of some bird species in particular growth types. For example, although logs were most abundant within old growth woodland, species such as the Brown Treecreeper (which are often closely associated with this resource), were more often recorded in epicormic regrowth and seedling regrowth. The Brown Treecreeper feeds on insects (especially ants) and differences in the types and abundance of invertebrates between growth types are also likely to influence many species of birds. The results of our study of birds have important implications for how different kinds of

26

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Small brown birds are sometimes called ‘LBJs’ by birdwatchers – standing for ‘little brown jobs’. Birds with these characteristics are in fact a group comprised of several species, with the thornbills being one of the most prominent members of this assemblage. The thornbills in our temperate woodland studies include the Brown Thornbill, Striated Thornbill, Buff-rumped Thornbill, Yellow-rumped Thornbill, Yellow Thornbill and Chestnut-rumped Thornbill. It takes quite a lot of field experience to quickly distinguish the body features and calls of these different species, as is required in our repeated field surveys of the woodland avifauna. Habitats such as replantings and riparian areas can be a particular challenge because on rare occasions almost all of the thornbill species can co-occur. In other cases, the identities of the most abundant thornbills can change markedly over time. For example, our study of woodland remnants surrounded by maturing pine plantations has shown that the Buff-rumped and Yellow-rumped Thornbills, which were dominant species at the start of the work in 1997, had largely been replaced by Striated and Brown Thornbills 18 years later. Photos by Warren Chad, John French, Greg Miles and Alwyn Simple.

vegetation growth forms might be best managed on a farm and we further discuss this topic in Chapter 7 of this book.

Which attributes of remnants are important for birds? When agricultural landscapes are cleared for human uses such as cropping and livestock grazing, there is typically a scatter of patches of native bush that remain uncleared or that regenerate after clearing. These patches vary in size, shape and other characteristics. Given this, we posed the question: •

Which attributes of woodland remnants influence their suitability as habitat for birds?

To answer this question, we focused on 13 woodland bird species of conservation concern that some other authors consider to be declining in agricultural landscapes (but see below). These included charismatic species such as

2 – Birds

27

the White-browed Babbler, Black-chinned Honeyeater, Superb Parrot and Restless Flycatcher.16 This work entailed completing detailed measurements of the vegetation at each of 138 woodland remnants in southern NSW. In addition, we collected data on the vegetation in the landscape surrounding each woodland remnant. We then counted woodland birds on these same 138 sites and used statistical analysis methods to identify which attributes of woodland patches influenced the occurrence of each of the 13 bird species.16 We have found that the occurrence of each bird species was strongly affected by both: (1) habitat variables that reflect the characteristics of the patch in which the site is located, and (2) landscape variables or attributes of the broader environment surrounding a given woodland patch. Habitat variables of particular importance included those in the ground layer (an abundance of leaf litter, an intact surface crust of mosses and lichens, and a scarcity of annual grasses) and overstorey (a scarcity of eucalypt dieback and an abundance of mistletoe). Landscape variables strongly affecting site occupancy included the number of paddock trees and the area of native grass within 500 m of a site.16 In addition, many bird species of conservation concern were strongly associated with regrowth woodland – a finding consistent with our other studies of birds in agricultural landscapes (see above).20 Importantly, we found that each bird species responded to a unique set of features of the vegetation cover and structure of remnant woodland patches as well as the attributes of the landscape surrounding those patches.16 In many ways this was expected because these (sometimes subtle) differences in habitat requirements is one of the ways in which different species co-exist in the same broad environment. These differences in habitat requirements also explain why woodlands are such extraordinary places that support so many kinds of birds.

Which attributes of plantings are important for birds? A key question in restoring areas of native vegetation in agricultural landscapes is: •

Are some kinds of plantings better for birds than others?

This is an important question to answer because poorly established planting may not be effective – and could even be worse than having no plantings at all. To determine the features of a good planting, we have studied more than 60 plantings of different sizes, shapes and ages (since first being established) on the South West Slopes of NSW.15 We found that the plantings likely to support the greatest number of bird species were those that: (1) were block-shaped rather than linear strips; (2) were located close to other plantings or large patches of native vegetation; (3) were established around paddock trees; (4) supported many clumps of mistletoe and large logs; (5) were subject to little or no grazing by domestic livestock; and (6) were located in gullies and around watercourses rather than on slopes or ridges15 (see Fig. 2.3).

28

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Can poorly planned and established plantings make it worse? Sometimes a poorly planned planting can make things worse for native birds and farmland conditions. Very narrow strip plantings increase the amount of suitable habitat for hyper-aggressive native birds such as the Noisy Miner that drive away other species of (smaller) native birds. Similarly, plantings established with exotic tree species tend to be attractive for exotic pest bird species such as the Common Starling and House Sparrow. What can be done to prevent these kinds of problems? The best solution is to establish wide plantings of native trees in the first place. Where narrow strips of exotic trees have previously been established, then the problem might be reduced by adding additional rows of native trees to widen the planting.21

Fig. 2.3.  Key features of plantings that will have increased value as habitat for native woodland birds.

2 – Birds

29

Plantings are a critically important vegetation type in farming landscapes. They support different assemblages of birds than other kinds of vegetation such as old growth woodland remnants. Some birds such as the Flame Robin are significantly more likely to inhabit plantings than other kinds of vegetation. Plantings should therefore be considered to be among the important vegetation assets that can be added to, and/or maintained on, a farm. Photo by Damian Michael.

Many species were more likely to occur in large plantings, although these patch size effects largely disappeared once we had considered how much native vegetation and/or the area of other plantings occurred in the surrounding 0.5–1 km. The Grey Fantail and Rufous Whistler are examples of species that exhibited this kind of response. Some species showed the opposite effect – the Noisy Miner was one of these species and its occurrence was markedly reduced in large plantings. Other factors that had an important effect on birds included the structure and composition of the understorey vegetation. As an example, the White-plumed Honeyeater was most often recorded in plantings with large amounts of wattle in the understorey. The Noisy Miner exhibited the opposite effect and responded negatively to the prevalence of understorey wattle.15 Yet other effects that we identified were related to the kinds of management within plantings. For example, grazing pressure reduced the likelihood of occurrence of the Superb Fairy-wren and the removal of dead shrubs had a negative effect on the White-browed Woodswallow.15

30

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Mistletoe is an important resource for temperate woodland birds. Several species are strongly associated with mistletoe such as the Painted Honeyeater and the Mistletoebird. Woodland patches and plantings that lack mistletoe are far less species rich than equivalent areas where mistletoe is common. Experiments where mistletoe has been removed from woodland patches have resulted in a significant reduction in bird species richness. Photo by Dave Blair.

We recognise that it may not be possible to establish block-shaped plantings or other kinds of wide (rather than narrow linear) plantings on some farms. This led to the question: • Are there any other aspects of the geometry of plantings that can promote their value for bird biodiversity? To answer this question, we compared the bird fauna of block-shaped plantings, isolated strip plantings and connected strip plantings.22 We found that the lowest bird species richness occurred in narrow-strip-shaped plantings that were isolated from other plantings. In a surprising result, narrow-strip-shaped plantings that were connected to other plantings supported as many species as block-shaped plantings. The intersections of plantings, in particular, were characterised by high levels of bird species richness.22 The results of the ‘intersection’ study have important implications for farm managers because if it is not possible to establish wide, block plantings, then many of the benefits of such kinds of planting designs can be emulated by connecting strip-shaped remnants. This can be particularly useful where plantings are established around the margins of adjacent grazing and/or cropping paddocks.22

2 – Birds

31

Determining which attributes of plantings influence their habitat suitability for birds is important for many reasons. In particular, this new knowledge highlights where revegetation efforts might be best located and what attributes characterise plantings that will be most effective for biodiversity.

Birds and travelling stock reserves Travelling stock reserves (also sometimes called travelling stock routes) are among the least disturbed parts of agricultural landscapes in eastern Australia. The travelling stock reserve network was established more than 150 years ago to facilitate the movement of domestic livestock between properties and to markets.23 Travelling stock reserves have many important cultural and heritage values for both Indigenous and European people.24,25 Travelling stock reserves are assumed to be valuable for biodiversity conservation because their periodic use for livestock grazing has meant that some have generally escaped vegetation clearing and prolonged set-stocking26, although the travelling stock reserve estate contains sites in varying degrees of degradation ranging from relatively low to severe. A key question then is: •

How important are travelling stock reserves for bird biodiversity?

We tackled this question in the Murray and Riverina regions of southern NSW by selecting patches of remnant woodland on farmland and then comparing them

Not all species are strongly associated with woodland tree cover. The Brown Songlark is one of these species. The distinctive, almost machine-like ‘mechanical’ calls of this bird can often be heard from pastures and even croplands. However, the species requires pastures and cropped areas characterised by structurally complex vegetation; birds are absent from simplified pastures. Photo by Ulf Gotthardsson.

32

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

House Sparrows are an ‘English import’, brought to Australia by white settlers to remind them of the ‘home country’. These birds are strongly associated with human infrastructure such as woolsheds, feedlots, homesteads and other buildings. They are uncommon elsewhere on farms, particularly in plantings and woodland patches dominated by native vegetation. The rate at which we have been recording this species in our long-term surveys has been declining markedly over the past decade – a pattern consistent with what has been observed in the United Kingdom and Europe where these birds originated. The House Sparrow does appear to be sensitive to drought, although population declines have taken place both during and outside of drought periods in Australia. Prolonged drought is obviously not a driver of decline in the United Kingdom and Europe. This suggests that other factors are having an impact on the House Sparrow, with the impacts of pesticides being proposed as one of the drivers of decline in the United Kingdom and Europe. It is not known whether pesticide use is also having impacts on the House Sparrow in southern Australia. Photo by Dan Florance.

with woodland in travelling stock reserves. In the Murray region, we identified 85 temperate woodland sites on private land for survey. We then selected 16 field sites within travelling stock reserves that were nearest the farms on which our 85 field sites on private land were located. This avoided bias in favour of any particular condition or management regime within the travelling stock reserves. We employed a similar site selection method in the Riverina region where we established 100 woodland sites on private property and an additional 16 sites within travelling stock reserves. We completed repeated surveys of birds at each of the 217 sites in the study and this led to a large dataset in which we were able to compare the biodiversity of the two broad kinds of sites. We found that, in comparison with the temperate woodland remnants surveyed on private land, travelling stock reserves tended to support more species of birds as well as more species of birds of conservation concern (such as the Red-capped Robin and the Brown Treecreeper). However, our

2 – Birds

33

results were not always consistent between the two regions. For example, travelling stock reserves supported more bird species and species of conservation concern than those sites on private land in the Murray region, but this was not the case for the Riverina region. As examples, in the Murray region, we were significantly more likely to record the Rufous Whistler and the Red-capped Robin in travelling stock reserves than on private land, but such patterns did not occur in the Riverina region. The reverse result was found for the Grey-crowned Babbler, which was significantly more likely to occupy sites in temperate woodland located within travelling stock reserve sites than on private land in the Riverina region. We did not seek to identify factors that may account for the observed differences in responses of biota between travelling stock reserves and other woodland remnants on other kinds of land tenure. Likely factors would include (among others) level of disturbance, size, and position in landscape.

The Superb Parrot is an iconic species in many areas of temperate woodlands of southern NSW. The future of populations of the species has been subject of debate and controversy, especially as populations of large old scattered paddock trees are in rapid decline in many agricultural landscapes. These trees are key nesting habitat for the Superb Parrot. Despite concerns for the future for the Superb Parrot, long-term data from our repeated field surveys have indicated that the Superb Parrot is being recorded more frequently and on more farms than it was 15 years ago. The reasons for the spectacular increase remain unknown, but one possible explanation is that trucks carrying grain now must cover their loads. Once common roadside spills of grain are now rare, and large numbers of birds are no longer killed in collisions with vehicles. It was not uncommon to see the crumpled bodies of 10–20 birds killed in this way, but this is fortunately now quite rare. This is important because adult mortality is often a key driver of population trends in long-lived organisms such as whales, elephants and large trees. The Superb Parrot seems likely to be no exception. Photo by Geoff Brown.

34

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Pines and woodland patches An increasing amount of the timber and pulp used to make paper and packaging in Australia is coming from plantations rather than native forests. This has resulted in increasing pressure to establish plantations such as those of Radiata Pine on farmland. The changes in land use practice led us to pose the question: •

What are the effects of broad-scale plantation establishment on birds?

We have considered this question in several ways. First, we conducted a global analysis to examine what happens to biodiversity when land is converted from pastures to plantations, including those dominated by exotic softwood pine trees. The result of this analysis indicated that the diversity of bird species typically increases, although open country birds are generally replaced by closed forest bird species.27 In contrast, for other groups, ranging from mammals and reptiles to invertebrates and plants, overall levels of biodiversity are little different between pastures and tree plantations.27 The second way we have examined the issue of how bird biodiversity changes when plantations are established was to implement a large-scale experiment to document the changes in species that occur when patches of remnant woodland are surrounded by maturing stands of Radiata Pine. The Nanangroe Plantation Experiment has been running since 1997 and it has quantified the changes in birds (and other groups of animals) that have occurred over the past 17 years as grazing land has been converted to plantation-dominated areas. Some fascinating patterns of bird response have been identified. The primary change has been that several forest-associated birds have colonised the pine plantation stands and then spilled over into the adjacent woodland areas. ‘Invading’ (native) forest bird species include the White-browed Scrub-wren, Rufous Whistler, Grey Fantail, Superb Lyrebird, Satin Bowerbird and Eastern Yellow Robin. At the same time, several woodland-associated birds and open-country species such as the Willie Wagtail, Brown Treecreeper and Eastern Rosella have declined or been lost from the study system.28–30 The changes in the overall bird assemblage throughout the duration of the study have been quite marked. Initially in 1997 (and before the first stages of plantation development), the bird assemblage was a classic woodland and open country one. After 5–7 years, the study area was characterised by a unique blend of woodland and forest birds; one that was not seen in nearby eucalypt forest areas, nor in nearby woodland regions. This unique forest-woodland assemblage was what has been dubbed a ‘novel ecosystem’.31 That is, an ecosystem comprising unique groups of species that have not previously been recorded in a given area. After just another 5 years (by 2012), the bird assemblage had changed yet again, and a large proportion of the woodland and open-country birds had disappeared and the area was dominated primarily by forest-associated bird species. The novel ecosystem was therefore a temporary aberration, lasting just a few years. Perhaps

2 – Birds

35

There are many birds of conservation concern that occur in temperate woodlands. Numerous scientists, farmers, land management practitioners and policy makers have rightly expressed great concern about the future of these species. However, what have been the changes in populations of these birds over time? The answer to this question has been elusive because there are precious few long-term studies that allow us to make definitive statements about the population trends of birds. Our long-term studies in southern NSW indicate that some bird species of conservation concern are doing well and have been increasing over the past decade. Examples include the Rufous Whistler and Superb Parrot. Others appear to be unchanged during this time; for instance, the Brown Treecreeper and Scarlet Robin. Yet others are clearly declining, sometimes precipitously such as the Varied Sitella, Crested Shrike-tit and the Black-chinned Honeyeater. However, it is also clear that the trend patterns we have observed are not always consistent across all regions. For example, increases in populations of the Brown Treecreeper in some regions are not matched elsewhere, where the species appears to be stable. (Pictured: (top) Rufous Whistler and (bottom) Varied Sitella). Photos by Dave Jenkins.

36

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Travelling stock reserves are an absolutely critical part of agricultural landscapes for conserving woodland biodiversity. They have been subject to less clearing and lower levels of livestock grazing pressure than elsewhere in agricultural landscapes. Most travelling stock reserves occur in flat valley floors, which are the areas most targeted for land conversion to cleared or semi-cleared paddocks and croplands. Travelling stock reserves provide essential habitat for a wide range of plants and animals and are also pivotal in connecting populations distributed across agricultural landscapes. Our studies of travelling stock reserves show that they can support higher levels of vertebrate species richness than woodland in other parts of agricultural landscapes. However, their value for biodiversity is dependent on how well they are managed because they can be degraded as quickly and badly as woodlands elsewhere in grazing and cropping environments. It is critically important that travelling stock reserves are not sold, as has recently been proposed. Photo by Dave Blair.

just as interesting is that although the vegetation in the patches being studied is dominated by woodland trees such as Yellow Box, Red Box, White Box and Blakely’s Red Gum, the bird assemblage is a forest-associated one. The ‘take-home’ message from the Nanangroe study is that, although the overall bird species richness has remained largely unchanged since 1997, the identities of the species that comprise the bird assemblage has undergone comprehensive change. The most obvious change has been from a largely woodland bird dominated assemblage to a predominantly forest bird assemblage. The transition from a woodland bird assemblage to a forest bird assemblage has resulted in some interesting replacements of particular species by other closely related species from the same guild of birds (a guild can be loosely defined as a group of species with similar diet, foraging strategies and sheltering or nesting requirements). For example, the woodland-associated Willie Wagtail has been replaced by the forest-associated Grey Fantail in many of the woodland patches surrounded by stands of mature pine. Similarly, the Buff-rumped and Yellowrumped Thornbills have been largely replaced by Brown and Striated Thornbills.

2 – Birds

37

A closer look at species change through a ‘functional’ lens Another way to look at the bird assemblage is through the lens of traits; that is, the particular diet, foraging strategy or nesting requirement of each species. The mix of traits in a bird assemblage is called ‘functional diversity’, and although likely to increase with the total number of species, this is not always so. Interestingly in Nanangroe, the total number of bird species present in the woodland patches stayed steady as the pines matured. But was this the same for functional diversity? The answer is no! Over time, functional diversity decreased, particularly in patches completely surrounded by pine. This reduction in the mix of species traits in the bird community was linked to a shift away from solitary or pair-forming, openwoodland species to flocking forest-associated species that feed on nectar and invertebrates.34 But why may this have happened? The pine plantation may act as a barrier to open-country birds, preventing them from finding, moving through, or colonising woodland patches that are completely surrounded by pines. On the other hand, the pines may change available food resources and attract new, forest-associated, species to the patches. These intriguing results would not have been known if we had looked only at the total number of species – a useful reminder of the importance of studying underlying mechanisms and to care ‘who’ each bird is.

Recent work on patterns of co-occurrence among closely related species indicates that competition is the most likely mechanism underpinning the replacement of one species by a closely related member of the same guild.32 But not all guilds were characterised by strong patterns of competition. For example, the Golden Whistler and Rufous Whistler often co-occurred in the same patches of woodland and, unlike other sets of closely related birds such as the thornbills, showed no evidence of competition.33 There are some other intriguing results from our long-term experimental study in the Nanangroe region. One of these is that patterns of co-occurrence among closely related species were influenced by the size of woodland patches. For example, the Crimson Rosella and Eastern Rosella co-occurred in large patches but not in small patches.32 These and other results suggest that the transformation of former semi-cleared agricultural areas into plantation dominated landscapes leads to quite complex changes in assemblages of birds and some of these changes are very difficult to predict. Much of our work in the Nanangroe region has focused on the patterns of occurrence of different species of birds in the patches of remnant woodland surrounded by pines. But an interesting additional question is: • Is it possible to identify the ecological processes giving rise to patterns of bird species change and co-occurrence in woodland patches surrounded by stands of Radiata Pine?

38

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

It is clear that the Nanangroe plantation is home to many large predatory birds such as the Australian Raven and Australian Magpie, both of which take the eggs and nestlings of smaller bush birds. Therefore, nest predation appears to be an important mechanism affecting the patterns of occurrence of species.

Bird responses to total vegetation cover at different scales Patches of native trees and shrubs are the most visible and easily recognised natural features of cropping and grazing environments. The amount of tree cover is now also easily measured using satellites and aerial photography. We know that many woodland birds are so named because patches of woodland provide their primary habitat. Two questions that follow from this are: •

Does the total amount of native woody vegetation cover influence the diversity and abundance of native birds? And if so:

• •

Does the relationship between cover and bird occurrence change when it is examined for individual sites (i.e. for a particular remnant or planting), across whole farms or across landscapes? Are there threshold or breakpoint relationships between the amount of vegetation cover and bird occurrence? (See Box on p. 41)

Sites are areas that span 1–10s of hectares, farms correspond to ~1000 hectares, and landscapes ~10 000 hectares. Therefore, this work is examining what are termed spatial scale effects.35 Answering these questions is important for vegetation management, because it tells us about what might happen to biodiversity as we begin increasing the amount of vegetation cover. It also helps guide where we might best target restoration efforts – on farms or in landscapes with presently low levels of vegetation cover or those farms or landscapes with high levels of cover? It also provides insights into the scale at which we might best do restoration – at the site level, farm level or landscape level. Our work at different scales is producing fascinating results. First, the diversity of woodland birds increased significantly with the amount of woody native vegetation cover at each scale. That is, at the site level, farm level and landscape level. On average, we found that every doubling in percentage vegetation cover resulted in an increase of 3.1, 2.3 and 0.7 bird species per landscape, farm and site, respectively. There also were similar positive relationships between the number of species of conservation concern and the amount of native vegetation cover at all three scales that we examined.35 Therefore, the amount of native vegetation cover proved to be a useful (although still rather crude) general indicator of the likely richness of bird species in a given site, on a particular farm, or across a landscape.

2 – Birds

39

Many ornithologists and land managers have expressed concern over the fate of remaining populations of the Grey-crowned Babbler. Travelling stock reserves are especially important environments for colonies of this species, and especially those that have been well managed and grazing pressure is periodic and infrequent. Our field data indicate that travelling stock reserves in the Murray region of southern NSW have particular value for the Grey-crowned Babbler. This species appears to respond strongly to revegetation programs and the hope is that active restoration efforts on many farms throughout the temperate woodlands also will eventually secure populations of this highly charismatic bird species. Photo by Warren Chad.

Second, and a factor complicating the direct use of vegetation cover as a crude indicator of bird diversity, was that effects of vegetation cover at each scale was influenced by the amount of cover at other scales. For example, the number of birds at a site was influenced not only by the amount of vegetation cover at that site, but also the amount of vegetation cover on the farm in which the site was located, as well as in the landscape in which the farm was located. The highest number of bird species was likely to be found at sites with a large amount of cover on farms with high cover and located within landscapes with high cover. The reasons for this result remain unclear at this stage but they may be associated with the influence of vegetation cover on the dispersal of individuals between woodland patches.35 A third finding from this work was that the shape of the curve for species diversity–vegetation cover relationships typically increased steeply at low levels of vegetation cover (see Fig. 2.4). This is called a ‘curve of diminishing returns’ and it means that absolute gains in bird biodiversity for a ‘unit increase in vegetation cover’ are greatest at relatively low amounts of vegetation cover.

40

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Fig. 2.4.  The relationship between the amount of native vegetation cover and richness of bird species. Curves of this shape are sometimes called ‘curves of diminishing returns’ (see text). (Based on data in Cunningham and colleagues 2014).35

The preceding work in this section describes the results of work focusing on overall diversity (richness) of individual bird species or the total number of species of conservation concern. But what about the responses of individual species of birds? We therefore reframed the questions outlined above as: • Does the total amount of native woody vegetation cover influence the occurrence of individual species of native birds? And if so: • Does the relationship between cover and the occurrence of individual bird species change when it is examined at the site, farm or landscape scale? We used the same approach to examine the relationships between the amount of vegetation cover and the occurrence of individual birds at the site, farm and landscape level.1 Again, some quite unexpected, but nevertheless important, results were derived from this work. For most woodland birds, there were strong positive relationships between their occurrence and the existing amount of cover at the site, farm and landscape scales. The reverse was true for most open-country birds such as the Brown Songlark, which is a native bird that typically inhabits intensively

2 – Birds

41

Are there ‘threshold’ levels of vegetation cover for native birds? Ecological theory suggests that there should be thresholds or critical breakpoints in the relationship between the amount of native vegetation cover and the diversity of bird species. That is, when the amount of native vegetation cover drops to a particular level (e.g. 30% of a landscape), then the diversity of bird species will collapse rapidly. Identifying if such thresholds occur and the cover levels at which they exist is crucial for guiding which landscapes to target for restoration and conservation management. We sought to determine threshold responses for vegetation cover in our decadelong datasets on birds in the South West Slopes region. Some authors have suggested that 30% cover represents a key threshold level,37 whereas others have argued that 10% is the threshold level below which accelerated losses in bird species diversity will occur.38 Interestingly, and despite detailed and extensive statistical analyses, we found no evidence for any threshold relationships for richness of bird species at any scale – at the site, farm or landscape level.35 Nor was there evidence of threshold or critical breakpoint relationships for any individual species of bird at any of the three spatial scales that we examined.1 Our failed efforts in finding threshold relationships were unlikely to be due to a lack of field data because the survey information that underpinned the analyses comprised repeated counts of birds between 2002 and 2012 on 184 sites, 46 farms and 23 landscapes. Although our lack of ‘success’ from a scientific perspective may seem frustrating, in many respects the paucity of threshold relationships is a positive outcome for environmental management in agricultural landscapes. This is because our findings suggest that a large number of species will continue to persist (at least in the short to medium term) within landscapes that have relatively limited amounts of cover, such as between 10 and 30%. In addition, our results indicate that efforts to increase vegetation cover, even in comparatively highly cleared areas, should have positive benefits for bird biodiversity.

cropped paddocks. More complex responses were seen for yet other species of birds. For example, the Superb Parrot was most likely to be recorded in heavily cleared cropping landscapes characterised by low levels of native vegetation cover. However, the species responded positively to sites with high levels of cover – indicating marked differences in response to vegetation cover at different scales (see Box above). These findings fit neatly with what is known about the ecology of this iconic Australian parrot in that birds feed so widely on seeds from grain crops but then nest in large old hollow-bearing trees, often where there is cover provided by surrounding vegetation.36 The preceding paragraphs described bird responses to the existing amount of native vegetation cover. However, one of the most striking changes in the agricultural environments on the South West Slopes has been the marked increase

42

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

A parrot with a difference – the Superb Parrot The Superb Parrot is without doubt one of the most spectacular birds in the agricultural landscapes of southern NSW. Brilliant green and gold colours and raucous calls by flocks of these beautiful birds make the Superb Parrot an excellent addition to any bird list on a farm. But the Superb Parrot is different from many other birds in a range of interesting ways. First, it is more of a bird of croplands than dense areas of woodland making it quite different from many other woodland birds that are closely associated with heavily wooded areas. Second, although the Superb Parrot remains a species of conservation concern, it is not a good indicator of the presence of other birds of conservation concern. In fact, it is what we have termed an anti-surrogate or anti-indicator in that typically where it occurs there will be few other bird species of conservation concern.39

in the amount of native vegetation cover over the past decade. More than 3.5% extra woody vegetation cover has been added across the region in the last 10 years, with some farms and landscapes characterised by many new areas of planting and natural regeneration. Some farms support more than 10% more cover than they did 10 years ago! These changes in native vegetation cover led us to pose the question: • How have birds responded to these impressive and positive changes in vegetation cover?

Like its close relative, the Grey-crowned Babbler (see photo on p. 39), the White-browed Babbler also nests in groups and also makes numerous stick nests – often a sign that birds are present nearby, even though they are not seen or heard. These nests are sometimes used by other animals such as the Common Ringtail Possum (see photo in Chapter 3), which also constructs similar kinds of nests (called dreys). The habitat preferences of the White-browed Babbler include areas of dense vegetation characterised by shrubs and mistletoe. Photo by Chris MacGregor.

2 – Birds

43

The answer to this question – like so many questions in ecology – is complex and multi-faceted. This is because it depends on which species of birds are being considered and the scale at which they have responded. For example, birds such as the Rufous Whistler responded positively to increasing vegetation cover but primarily at the site scale and not the farm or landscape scale. Conversely, open country birds such as the Noisy Miner and the Magpie Lark responded negatively to the increase in native vegetation cover – at both site and farm scales. In yet further complexity, birds such as the Jacky Winter responded negatively to the increase in cover over the past decade, even though they are more likely to occur on farms and in landscapes with high levels of cover. This seemingly contradictory result is explained by the fact the Jacky Winter generally prefers old growth woodland patches and avoids newly established plantings. Plantings contribute much of the new area of expanding vegetation cover and are established primarily on heavily cleared farms where old growth woodland was removed and is currently limited in extent.1 As we discuss in Chapter 7, the results of our work on relationships between the amount of vegetation cover and the diversity of birds have important

Remote, motion-sensitive camera can be used to learn many new and interesting things about particular species. For example, predation is common but rarely observed. Cameras can help change this. We have used cameras to identify which species prey on the quail eggs we deposited in artificial nests. The Australian Magpie (pictured), Australian Raven and the Grey Butcherbird were revealed to be the most active nest predators.

44

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Pied Butcherbird is a common inhabitant of woodland habitats and our field surveys of birds have produced many records of this species. There are many species of butcherbirds in Australia, including a recently described new species from the Kimberley region in north-western Western Australia. All of the species in the group share the habit of skewering their prey on a sharp branchlet much like a butcher hangs meat from a butcher’s hook, hence the common name. Photo by Patrick Kavanagh.

implications for programs that aim to increase the amount of vegetation cover on farms or in landscapes.

Bird occurrence over time Many people have been deeply concerned about the status of many woodland birds, with some authors suggesting that as many as half of current species are at risk of being lost by 2050. Almost 500 scientific articles in Australia have focused on this topic. Despite the large amount written, remarkably few articles actually contain long-term field data to determine whether particular birds of conservation concern are (or are not) showing signs of decline.40 To explore this issue, we examined patterns of long-term change in 66 species of birds in woodland eucalypt remnants between 1998 and 2009.41 We recorded 116 species of birds during repeated surveys. Of these, there were sufficient data to analyse the long-term

2 – Birds

45

Many Australians associate cuckoos with clocks and Europe. But this continent supports an extraordinary variety of cuckoos, from relatively small bronze-cuckoo species that parasitise the nests of thornbills (see photos) to the huge channel-billed cuckoo (vaguely reminiscent of a South American toucan) that lays its eggs in the nests of currawongs and wattlebirds. Plantings can be hotspots for cuckoos because these restored environments support large numbers of potential hosts – thornbills and wrens. In addition to daytime counts of birds, our field surveys also entail spotlighting of remnants and plantings. It is at these times that cuckoos can sometimes be heard calling well into the night – perhaps as a strategy to continue to maintain links between mated pairs of birds in case they should chance upon an empty nest in which to lay an egg. An alternative or additional explanation may be that calling at the beginning or the end of the breeding season might be to do with night-time migration. That is, males that have already set up a breeding territory may call to attract a migrating female as she's passing over, or birds that are ready to migrate call to make contact with other migrating individuals. (Pictured: (clockwise from top left) Fan-tailed Cuckoo, Shining Bronze-cuckoo, Pallid Cuckoo, Horsfield’s Bronze-cuckoo). Photos by Warren Chad.

trends in reporting rate of 76 species. The results were most unexpected – especially relative to what many people had forecast might occur and particularly because much of the duration of the investigation coincided with the Millennium Drought. In fact, only four of the 76 species analysed (~6%) exhibited a significant decline in reporting rate. Two of these were exotic species (the Common Starling and the House Sparrow) for which a decline is a positive environmental outcome. More surprisingly, 32 species (42%) exhibited a significant positive increase in reporting rate. These included several bird species of conservation concern such as the Brown Treecreeper, Varied Sitella, Rufous Whistler and Jacky Winter.41

46

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Notably, some of the general findings from this long-term work are broadly consistent for many of the same species in other large-scale, long-term studies we have conducted in agricultural landscapes of eastern Australia. The reasons for these very positive results remain unclear, although they may be associated with a general increase in native vegetation cover that has been occurring in some parts of the wheat-sheep belt of southern NSW over the past decade. However, it is unlikely there is a simple explanation for our results as illustrated by the facts that: (1) there is little evidence of systematic cross-species responses to environmental conditions such as wet and dry years; (2) although there are strong similarities in trend patterns among studies in some regions in south-eastern Australia, there are marked differences in results between others; and (3) there is an absence of apparent associations between trend patterns and life history of birds, including a lack of congruence between the findings of our study and previous forecasts by other workers of bird species likely to decline or likely to increase in temperate woodlands.41

The Jacky Winter is a robin and closely related to the Scarlet Robin and Flame Robin that also occur in temperate woodland environments. It is not at all related to the robins found in North America and Europe. A lot of new insights into the ecology and conservation of the Jacky Winter have been gained from research over the past few years. It is a bird of conservation concern that is most often found in relatively intact woodland patches with some areas of shrubby understorey. It appears to be sensitive to intensive livestock grazing where the understorey is degraded or lost, most probably because this limits available nesting sites and places where they can most effectively forage for insect prey. The Jacky Winter is a useful species to find in a woodland patch, because our work on woodland bird assemblages shows that many other bird species often co-occur with it. The data therefore suggest that the Jacky Winter is a member of relatively intact species-rich bird assemblages. Photo by Marlene Lyell.

2 – Birds

47

Irrespective of the underlying ecological reasons for our findings to date, this work highlights the critical value of doing the hard work of actually counting animals in the field year after year to quantify what is happening in agricultural landscapes.

Do plantings get better with age? Many things improve with age. Is the same true for plantings? This led us to pose the questions: • •

Does the number of bird species increase with the increasing age of plantings? That is, do we see more bird species in old plantings than younger aged ones? Which species colonise plantings over time and do the identities of species occupying plantings change as plantings age?

The answer to these questions are not nearly as trivial as they might first seem. There is a surprisingly absence of answers because there are so few long-term studies

A Jacky Winter feeding its young. Almost all of the research on woodland birds to date has been short-term studies that record the presence of particular species. Longer term studies that quantify whether birds persist in an area and breed successfully is almost non-existent. Although it appears that small woodland birds are strongly associated with replantings, high levels of predation (e.g. by the Eastern Brown Snake) or nest parasitism by cuckoos may mean these places become ‘ecological traps’ that are colonised by birds that then fail to go on and reproduce. New studies that document which birds breed successfully have just commenced in an attempt to improve guidelines on the best kinds of plantings to establish and the key remnants to target for conservation and/or restoration. Photo by Dave Jenkins.

48

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Single, often seemingly isolated, paddock trees may appear at first glance to have limited value for conservation. This is far from the case. Paddock trees play many key roles for biodiversity conservation in woodland environments, especially for a wide range of bird species. They are used as stepping stones and assist animals in moving through landscapes. Paddock trees provide critical places for nesting and foraging, especially as they are often the largest and oldest trees in a given area and therefore support pulses of flowering and contain more large hollows than other trees in agricultural landscapes. Photo by Tabitha Boyer.

of revegetated woodlands. In addition, we know that planted areas typically support more bird species than a cleared or heavily grazed paddock – although some bird species such as the Brown Songlark and the Australian Pipit most often occur in such heavily modified areas. We documented what happens to the community of birds in over 50 different plantings over a 12-year period (from 2002 to 2013). Our work to date shows that the number of species found in plantings does indeed increase over time, but only in winter and not in spring when it has remained largely constant over the past decade or more. However, even in winter, the increase in the number of species has been rather small – on average just two more species in 2013 than 10 years earlier. Perhaps more striking has been that while the number of species has changed relatively little, the identity of the species has changed markedly. Over time, plantings are far more likely to be colonised by birds such as the Red Wattlebird and Noisy Friarbird, whereas others such as the Noisy Miner and Rufous Songlark that initially occupied young plantings rarely use them as restored areas mature. This means that the bird community that characterises young plantings is quite different from that which occurs in older aged plantings. This has some significant implications for how plantings might be best managed on a farm – a topic we will return to in the final section at the end of the chapter.

2 – Birds

49

A harsh, yet distinctive ‘spink-spink’ call ringing out through patches of temperate woodland highlights the presence of groups of the Brown Treecreeper. Many people have expressed great concern about the future of populations of the Brown Treecreeper. This is because it has a complex group social structure, a limited dispersal ability, and an affinity for areas with fallen timber (but which is often removed as part of ‘cleaning up’ paddocks). The Brown Treecreeper is sensitive to extensive Pine Plantation establishment and is replaced by the White-throated Treecreeper in woodland patches surrounded by exotic softwoods. The Brown Treecreeper has gone extinct with formal reserves such as Mulligan’s Flat in the ACT and subsequent attempts to re-establish populations have been largely unsuccessful. However, long-term data suggest that populations of the Brown Treecreeper have been increasing in some woodland regions in southern NSW and are stable in others. Photo by Dave Jenkins.

Birds and the Millennium Drought Much of our work has taken place during prolonged dry periods in Australia’s agricultural landscapes. An interesting question is: •

What have been the effects of major events such as the Millennium Drought on populations of birds?

Our work over the past decade has shown that many species do indeed undergo substantial declines during extended dry spells – the Sulphur-crested Cockatoo and Black-faced Cuckoo-shrike are two of several prominent examples. But not all birds decline during these times. For example, species of conservation concern such as the Brown Treecreeper have increased significantly during the Millennium Drought. It is not entirely clear why this has happened. For the Brown Treecreeper, which feeds predominantly on ants, dry periods often lead to more open ground

50

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The White-browed Woodswallow is a highly nomadic species. Good conditions following rain can rapidly trigger breeding and birds can nest almost anywhere – such as the old winch in this image – although dead trees appear to be preferred places to construct a nest. Plantings are important refuges for the White-browed Woodswallow during dry times. Photo by Damian Michael.

that can be colonised by ants. It is therefore possible that the Brown Treecreeper has access to more food during droughts, which may explain why the rate of reporting increased during the decade of the 2000s. However, this species also increased in landscapes and on farms where the amount of native vegetation cover increased during the same period, suggesting that an increase in available habitat might also have had a positive effect on this species over time by facilitating dispersal between woodland patches.1 Other species of birds such as the White-browed Woodswallow increased during the Millennium Drought. Unlike the Brown Treecreeper, the White-browed Woodswallow is highly mobile and nomadic and it seems likely that populations from drier and more westerly areas moved into the South Wales Slopes as the drought intensified. Notably, reporting rates for this species declined in 2010 and 2011 when wetter conditions characterised the post-drought period. Given the substantial changes in bird populations that are associated with droughts in Australia, an additional interesting question is:

2 – Birds

•

51

Are there particular attributes of woodland remnants that can mitigate local drought effects on birds? That is, are there features of the vegetation that influence the value of patches of woodland as drought refuges?

Answering this question is important because it helps prioritise areas for careful management to assist species conservation during droughts. Our analyses showed there were features of woodland patches that enabled such areas to better support bird populations during droughts. Patches with large amounts of mistletoe, fallen logs and limited tree dieback proved to be particularly and consistently important for a suite of bird species during the ‘Millennium Drought’ of 2001–2009. In addition, sites and farms with high levels of native vegetation cover proved to be particularly important, including for birds of conservation concern such as the Eastern Yellow Robin.42

Management interventions and birds There are several ways to improve environmental conditions on farms. These include (among many others): (1) reducing grazing pressure by limiting the number of stock or altering the intensity and timing of grazing; (2) actively controlling weeds and pest animals; (3) halting or reducing levels of firewood and bush rock removal; and (4) actively restoring areas of native vegetation by replanting. Other work (see above) has clearly demonstrated that the last of these

One of the calls made by the Willie Wagtail is considered by some to sound like ‘sweet pretty creature’. However, this belies the aggressive responses of this bird used to drive away intruders, including potential nest predators that are far larger than itself such as ravens, magpies and even the Wedge-tailed Eagle. This behaviour may be one of the reasons why it is widespread in farmland environments. Our long-term studies have indicated that the Willie Wagtail is lost from woodland patches when the surrounding landscape is converted from semi-cleared grazing land to Radiata Pine plantations. The Willie Wagtail is replaced in pine-dominated plantation landscapes by the relatively closely related Grey Fantail, which is also a member of the ‘flycatcher’ group of birds. Photo of Grey Fantail by Alwyn Simple, Willie Wagtail by Dave Jenkins.

52

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Gang-gang Cockatoo is an increasingly rare sight in temperate woodland habitats. It was uncommon 15 years ago when we first commenced our work, but it is now virtually never recorded in our extensive formal winter and spring surveys. Like many bird species of conservation concern in temperate woodlands, it also occurs in a range of other environments (such as high-elevation forests and tall wet eucalypt forests) where populations do not appear to be suffering the same declines. The reasons for the marked decline of the Gang-gang Cockatoo in temperate woodlands remain unclear and new research is urgently needed to determine why it is occurring. Such work is important so that the highly distinctive ‘squeaky door’ calls of the Gang-gang Cockatoo are not a lost sound from Australia’s temperate woodlands. Photo by Dave Blair.

– replanting – can have positive impacts on biodiversity. But what about other strategies? That is: • Do management activities lead to positive responses by native birds? We examined this issue in a major study in western Murray region of southern NSW where a conservation incentive scheme had been implemented as part of efforts to improve environmental conditions on farms. The incentive scheme provided landholders with funds to fence remnant vegetation and control the intensity of grazing by domestic livestock. Our study involved contrasting the vegetation and associated biodiversity on four kinds of sites – those where the incentive scheme had just been implemented, those where the incentive scheme had been in place for several years, those where there was no incentive scheme (that is, set stocking grazing with a production focus), and travelling stock reserves, which act as a kind of best condition benchmark as grazing pressure has been generally limited in these places for many decades (if not for much longer).

2 – Birds

53

The Mistletoebird, or flowerpecker as it is sometimes called, is found across the Australian mainland in most vegetation communities that support trees and shrubs. The female builds a pendulous nest made from the web of spiders and plant material, which is usually suspended from a thin branch in the tree canopy. As its name suggests, the Mistletoebird feeds on the fruits of various mistletoe species and, in doing so, plays a crucial role in spreading seed and maintaining populations of these particular parasitic plants. The Mistletoebird is absent from Tasmania. Some scientists have speculated that because mistletoe seeds pass through the gut of birds very quickly, the Bass Strait crossing may have been too far for birds to effectively disperse mistletoe from the mainland to Tasmania. Photos of Mistletoebird by Jeremy Wong, nest image by Mason Crane.

54

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The photo shows patch Nan09, a 9.9 hectare patch of Red Box/Yellow Box woodland that is surrounded by young stands of plantation Radiata Paine in the Nanangroe study. A 200 m long transect has been established within this patch and repeated surveys of birds have taken place every 1–2 years since 1997. Photo by Mason Crane.

The work has revealed some exciting new insights. Management interventions through the incentive scheme resulted in a substantial increase in the amount of ground cover, natural regeneration and shrub cover.43 These changes led, in turn, to changes in the bird fauna, with small bush birds that consume food other than seeds responding positively to the changes in vegetation cover associated with the incentive scheme. The most diverse bird community occurred in the benchmark travelling stock reserves, with the sites that had been converted many years ago to conservation management being the next best. This is a very positive finding, but it also suggests that altered management regimes will be needed over a prolonged period to continue to move the composition of the bird community on sites under incentive schemes closer to that characteristic of travelling stock reserves.

Are birds good indicators? Biodiversity is complex, in part because there are many different species and each one can have different requirements and vary in sensitivity to changes in the environment. Such diversity of species means that it is logistically and financially impossible to manage specifically for every individual species. One solution to this problem has been to select particular species to be targeted for management in the hope that other species also will benefit from actions taken to conserve the target

2 – Birds

55

Part of ANU research in the Nanangroe study has been to explore patterns of co-occurrence among closely related species within woodland patches over time. The Crimson Rosella and Eastern Rosella co-occur in large patches but not small ones. In contrast, the woodland-associated Willie Wagtail was replaced by the Grey Fantail as the pine plantations surrounding the woodland patches matured. Photos by Tobias Hiyashi.

species. The assumption is that the species targeted for management will be an ‘indicator’ of (or surrogate for) the occurrence and conservation of other species that are not the focus of management. This assumption leads to the critical question: • Are particular species of birds good indicators for other birds, or indeed other elements of the biota such as reptiles, mammals and invertebrates? The answer to this question is both yes and no. We have found that some species of birds of conservation concern (e.g. the Eastern Yellow Robin and Jacky Winter) are often good ‘indicator’ species in that they are typically found in places characterised by high numbers of other bird species, including many other bird species of conservation concern. This is most likely because they have similar requirements for habitat features such as the presence of a shrubby understorey, mistletoe and leaf litter.37 However, while some species of conservation concern are relatively good indicators, they are far from perfect. This is because the presence of no single species indicates the occurrence of the full suite of other birds in the agricultural ecosystems we have carefully studied. Moreover, our work has indicated that areas supporting many species of birds do not also support large numbers of species of reptiles, mammals or plants.37 In fact the opposite is often the case – rocky outcrops where many species of reptiles occur (see Chapter 4) are typically places where most species of birds are absent. This is most likely because

56

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

few bird species in temperate woodland regions forage or nest in habitats dominated by exposed or semi-submerged rocks.44 In summary, it is clear that the presence of some select species of birds can be a relatively good indicator of the likely presence of many other species of birds. However, their value as surrogates does not extend to all bird biodiversity and unfortunately fails badly when we explore the indicator value of birds for other groups of vertebrates such as reptiles.

Concluding comments A rich assemblage of native bird species is a welcome addition to any farmland environment. This not only because of the inherent beauty of such animals, but also because of the roles they play in maintaining ‘healthy ecosystems’ through pest control and pollination. A lot of our long-term research has focused on bird responses to the types, amount and condition of native vegetation on sites, farms and in landscapes. Another major focus of research has been on the effectiveness of interventions to improve farmland vegetation cover and condition. This research has indicated that good management (guided by good science) has produced positive outcomes for many native bird species. ‘Good management’ can encompass many different things from grazing control, limiting clearing, to establishing plantings, as we discuss in greater detail in Chapter 7.

3 Mammals

Introduction The mammal fauna of agricultural landscapes is rich and diverse – although significantly less so than either the bird or reptile fauna. Native mammals that occur in the regions we have monitored range from possums and gliders, flying foxes and bats, small micro-carnivores such as antechinuses and dunnarts, through to the Short-beaked Echidna, the Common Wombat (the world’s largest burrowing animal), and a suite of species of kangaroos. However, the native mammal fauna is far less diverse than it once was. An array of species that used to be common and widespread in these areas has disappeared from agricultural landscapes – sometimes just 100–150 years ago. Examples of lost species include bettongs, bilbies, quolls (or native cats) and a raft of other animals (see Box on p. 58). Yet, other species such as the Koala still occur in some scattered areas but are generally rare or absent in many others. While the native mammal is much less diverse than it once was, there are also many exotic species, some of which are serious pests in agricultural landscapes. These include not only the Red Fox, feral cat and European Rabbit, but also the feral pig, European Hare, House Mouse and Black Rat. Others such as the Red Deer and Fallow Deer are not yet considered to be serious pests, but appear to be spreading and increasing rapidly in number. If their populations are left unchecked they may yet create significant management problems. .

58

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Native mammals are disappearing The sad reality is that Australia’s mammal fauna is characterised by more species extinctions than on any other continent.45 A total of 28 species of mammals have been lost from Australia since European settlement. This is ~10% of the nation’s entire mammal fauna. By contrast, mainland North America (which is far larger than Australia) has lost just a single species.46 Many of the native mammal species that still persist in Australia are only just hanging on – some now occur in just 1–5% of the area of Australia that they formerly occupied at the time of white settlement. Australian desert environments have been the most heavily hit, with more than 30% of species absent. The temperate woodlands biome, where much of the work described in this book has been conducted, has fared little better. What mammals have been lost that should be there? The answer is a long list of now regionally extinct species. A classic example is the Greater Bilby, which most Australians regard as a desert animal, but for which there are records from woodlands in places such as Cootamundra, Henty and Lake George. Similarly, the Tasmanian Bettong was widespread and common throughout Australian temperate woodland. Indeed, it was once so common that just a century ago it was impossible to grow potatoes in the Canberra district because of the amount of digging done by these animals. Other charismatic animals such as the Koala and Spotted-tailed Quoll are now either extremely rare or locally extinct. The likely reasons for the losses of these species are varied and complex and range from deliberate hunting and persecution, competition with introduced herbivores, including rabbits and domestic livestock, predation by feral animals (especially the Red Fox and the feral cat), and increased frequency of high-severity wildfire. Does it matter that these species of mammals have been lost or have declined? The answer is a resounding yes! One reason it matters is that these animals are key part of Australia’s natural heritage. Another is that these animals occur nowhere else and we have a custodial responsibility to maintain viable populations of them. A third is that many native mammals play important ecological roles in woodland ecosystems. For example, digging animals such as bilbies and bettongs are widely referred to as ‘ecosystem engineers’ because their activities change ecosystems in fundamentally important and very positive ways. Digging by native mammals has been shown to significantly influence the effectiveness of rainfall infiltration, litter decomposition, plant growth and soil erosion.47

Much of our research and monitoring focus on mammals over the past 17 years has been on arboreal marsupials, although we do also have substantial datasets on other species of mammals observed during spotlighting surveys, as well as those detected in our large-scale nest box studies. Most of the content of this chapter pivots around research findings for possums and gliders, especially the threatened Squirrel Glider, although we also discuss some of our findings on exotic mammals such as the Red Fox and Black Rat.

3 – M a mm a l s

59

How mammals are studied? Field survey methods We use several methods to survey mammals on farmland. The primary one is spotlighting, which is obviously targeted at detecting nocturnal animals, particularly various species of possums and gliders. Different species are located by their ‘eyeshine’ (reflected from the spotlight) and then body size and movement patterns are used to help distinguish among the various possums and gliders. Spotlighting involves systematically scanning the trees and shrubs along the 200 m long transect we have established at permanent field sites. At the same time as possums and gliders are surveyed, we also record sightings of other animals such as the Red Fox, feral cat, and European Rabbit, as well as the Barn and Barking Owls and the Southern Marbled Gecko. We record various species of mammals in other kinds of surveys. These include our work on nest boxes, as well as mammals found under artificial substrates such as tin and timber that we use in studies of reptiles (see Chapter 4). Another survey method we have employed is stagwatching. This involves careful scanning of large old hollow-bearing trees, which are the den sites of cavity-dependent animals such as the Squirrel Glider.48,49 These large trees are watched in silhouette at dusk for an hour and the number and identity of animals that emerge from these trees is recorded. A substantial part of the work on the Squirrel Glider has used this method to determine where traps should be placed to capture animals and then fit them with radio-transmitters.

Habitat trees, paddock trees and arboreal marsupials – the case of the Squirrel Glider The Squirrel Glider is one of the most beautiful and charismatic mammals in the temperate woodlands of Australia. It has a long brushy tail and a distinctive black stripe along its back. The Squirrel Glider is an animal of considerable conservation concern, in part because it is dependent on large old hollow-bearing trees and populations of these trees are in steep decline across large parts of Australia’s wheat-sheep belt. Rapid losses of large old trees are not being countered by the recruitment of new cohorts of trees that will replace even a small fraction of those that are being lost.50 The rapid attrition of large old trees is occurring for a wide range of reasons including: deliberate culling for firewood harvesting; removal to facilitate cropping, destruction as a result of wildfire and/or prescribed burning; intensive grazing (which adds an oversupply of nutrients to the soil and kills eucalypts); and over-browsing by herbivorous insects such as the Christmas Beetle. In addition, many large old trees exceed several hundreds of years in age and are reaching the end of their standing lives. Previously, over many millions of years, as trees died, cohorts of newly regenerating trees would replace them and continue the processes of germination, growth, maturity and mortality that characterised woodland-

60

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Squirrel Glider is often considered as a ‘flagship’ species for woodland conservation and its persistence should be regarded as a broad indicator of ecologically sustainable grazing and cropping practices in farming landscapes. Populations of the Squirrel Glider are at risk of decline for a range of reasons, but particularly the loss of large old hollow-bearing trees, without which the species can’t survive. This species has been the target of intensive research by our ANU team over the past decade and many landholders are now doing a lot of work to try help better conserve these gliders, such as planting wattles (the gums of which are a key food source) and erecting nest boxes as artificial denning sites (in the absence of hollow-bearing trees). One of the most effective strategies for conserving populations of the Squirrel Glider is to prevent the loss of large old trees with hollows. This means not cutting them down for firewood, limiting burning around large old trees (because they are highly prone to being destroyed by fire) and promoting vegetation regeneration to provide new cohorts of trees to replace existing ones as they are lost. Photo by Katherine Tuft.

dominated landscapes. But the process of tree recruitment is now severely impaired because of intense grazing by domestic livestock, high concentrations of nutrients in the soil and a range of other factors. Given the problems occurring in populations of large old trees, coupled with the fact that such kinds of trees are an essential part of the habitat requirements of the Squirrel Glider, we posed the question: • What kinds of large old trees are those most likely to be used by the Squirrel Glider; that is, what characteristics of den trees and trees used by the species distinguish them from trees that are not used by the Squirrel Glider? New information gathered from answering this question is, in turn, an important part of developing strategies that will be effective for conserving this iconic species. The work on the Squirrel Glider entailed fitting radio-collars to

3 – M a mm a l s

61

The Sugar Glider is more often heard than seen, because it has a distinctive ‘yip-yip’ call reminiscent of a small dog. The Sugar Glider is the world’s most widespread marsupial and occurs throughout large parts of the Australian mainland and New Guinea, as well as several islands (e.g. Tasmania and the islands off New Guinea) where it has been introduced. The Sugar Glider is also now a popular pet in the USA. The Sugar Glider is an animal of great cultural significance for many people in New Guinea where it is believed to have magical powers and be a representative of the spirit world. The Sugar Glider and Squirrel Glider can be difficult to distinguish in the field, but there are clear differences in body size, facial shape, tail morphology and markings on the fur. The Sugar Glider is also a far more widespread animal with less specialised habitat requirements than the Squirrel Glider; it more readily occupies nest boxes and is even known to colonise stands of young plantation trees such as those dominated by exotic Blue Gums. Photo by Henry Cook.

62

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Common Brushtail Possum is now the most abundant species of arboreal marsupial in temperate woodlands. The species is a generalist and consumes a wide range of fruit, seeds, pollen, leaves and other kinds of food (including eggs and nestling birds when it can find them). Our long-term monitoring data indicate that the Common Brushtail Possum is increasing in temperate woodlands and expanded areas of native vegetation cover associated with replanting programs and passive natural regeneration appears to have benefitted this species. The Common Brushtail Possum’s strategy of breeding twice a year is likely to be one of the reasons for its success. Semi-independent young ride on their mother’s back until they leave the natal territory. The Common Brushtail Possum responds strongly to the control of feral predators such as the Red Fox, although it typically takes 5–8 years for population recoveries to be readily observed. The species also readily occupies nest boxes and is the mammal that we have most often found using these artificial hollows. Photo by Damian Michael.

animals and tracking them to their daytime den trees. Measurements were then made of the den trees, as well as randomly selected trees scattered throughout the areas where gliders were tracked.48,49 Analysis of field data gathered on the Squirrel Glider revealed that the species prefers to den in very large diameter eucalypt trees with numerous hollow branches. In addition, large old trees close to other large old trees are more likely to be occupied than isolated trees that are distant from other suitable trees. This result is likely to reflect the fact the individual animals swap repeatedly between nests in different trees. This kind of behaviour is typical of all species of possums and gliders. It appears to be designed to reduce the risks of being preyed on by owls and limit the number of parasites that infest their fur.10

3 – M a mm a l s

63

The approach used to analyse data from tracking the Squirrel Glider was to build a statistical model of the features of the trees used by animals. An unexpected result of this work was that the model was most accurate at predicting which trees were not likely to be used by the Squirrel Glider. The model was able to predict lack of use with 97% accuracy. The model can help identify trees that could be felled without a loss of critical habitat resources for the Squirrel Glider such as, for example, in areas proposed for urban development or widening of roads. It also could also be useful in assessing whether an area is unsuitable for translocating or releasing the Squirrel Glider or is an appropriate place to try to establish habitat for the species.49

Countryside elements and mammals – the special case of the Squirrel Glider An additional study on the Squirrel Glider explored the species’ use of four different components of the vegetation in agricultural landscapes – in particular, linear strips of vegetation along roadsides, patches of remnant vegetation, scattered paddock trees and plantings.51 These different kinds of relictual and often seminatural habitats in agricultural areas have been termed ‘countryside elements’ by researchers working on biodiversity conservation in agricultural environments elsewhere around the world such as in Costa Rica.52 Specifically, our study aimed to answer the question: •

Does the Squirrel Glider use different countryside elements in proportion to their general availability in the landscape, or are some elements favoured relative to others?

Our study of the Squirrel Glider showed that the species occurred regularly in all four of the different kinds of countryside elements, but that animals used woodland patches and scattered trees far more than their availability in the landscape. Squirrel Gliders forage in plantings but typically only in those restored stands that were adjacent to woodland remnants and areas of large scattered paddock trees. Although the Squirrel Glider searches for food within plantings, it never dens in them.51 This is most likely because plantings are largely dominated by young trees where there are no suitable nesting sites for the species. A further important result from the countryside element study was that the home range of animals varied depending on which elements were used most often. Animals with the smallest home ranges were those that primarily used areas dominated by large old scattered trees. A small home range is often regarded as an indication that the area is of high habitat quality. In contrast, animals that used roadside reserves and woodland patches had large home ranges. The reason for this unexpected result remains unclear but it may be associated with the fact that areas of scattered trees support the largest trees remaining in agricultural landscapes.

64

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

A gentle twittering call can often reveal the presence of the Common Ringtail Possum during spotlighting surveys. The Common Ringtail Possum eats a wide range of food including leaves, seeds, flowers and fruit. The species is one of the main prey items for exotic predators such as the Red Fox and feral cat. The Common Ringtail Possum responds strongly to fox control programs, but our long-term datasets also suggest that populations have increased over time in concert with efforts to increase the amount of native vegetation cover through planting and natural regeneration. The occurrence of the Common Ringtail Possum is strongly associated with particular kinds of woodland, especially stands that are dominated by White Box, Grey Box and Red Stringybark. The foliage of different eucalypt tree species vary in the quality as a food source for the Common Ringtail Possum and this is likely the reason underpinning differences in the abundance of animals between different woodland vegetation types. Some areas of temperate woodland can support extraordinary densities of the Common Ringtail Possum; we have recorded up to 15 individuals along a single 200 m spotlighting transect. An equivalent number of Common Brushtail Possums also occurred at the same site, along with Sugar Gliders and Squirrel Gliders, suggesting the occurrence of high-density population hotspots for animals in particular parts of woodland landscapes. Photo by Damian Michael.

These places are also the flattest and most productive areas in the landscape. Trees in these areas typically support the largest hollows and the biggest and deepest canopies where animals are most likely to find both suitable nesting sites and abundant food resources (e.g. flowers, pollen, sap and insects).51 The results of the work on countryside elements have clearly indicated that all of the various relictual habitats that remain within agricultural landscapes have some habitat value for the Squirrel Glider. Most importantly, areas of scattered paddock trees are often not recognised as being important wildlife habitat by many

3 – M a mm a l s

65

land managers and farmers. Crane and colleagues demonstrated that parts of farms with scattered paddock trees are disproportionately important for the Squirrel Glider, and careful management of these areas is necessary given the array of current threats to these trees.51

Mammals in nest boxes The loss of large old hollow-bearing trees is a pervasive problem in a very large number of Australia’s ecosystems, including many of the nation’s agricultural environments. The establishment of nest boxes has often been recommended as a strategy that attempts to tackle this major problem. Given this, we sought answers to questions such as: •

How effective are nest boxes for mammals? Will nest boxes provide a useful lasting alternative to large old hollow-bearing trees?

Many studies in Australia and around the world have examined these questions, with varying results. Our research group has explored the nest box effectiveness

The Yellow-footed Antechinus is a 20–75 g micro-predator that is widespread throughout the temperate woodlands of southern Australia. The species eats a wide range of insect prey but is also known to capture, subdue, kill and eat small lizards, and house mice. The Yellow-footed Antechinus is more diurnal than many other Antechinuses and we often observe it early in the mornings during bird surveys, especially in areas with scattered fallen timber. Photo by Mason Crane.

66

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

issue with a focus on how they are used by hollow-dependent animals in agricultural environments. We described our preliminary findings for birds in the previous chapter (see Chapter 2) and in the remainder of this section we discuss the results to date for mammals. These findings are based on several long-running studies in which nest boxes have been installed in plantings and in woodland remnants on roadsides – largely as an offset for the widespread tree clearing that was associated with the upgrading of the Hume Highway in southern NSW. To date, the following initial findings have been made: • Nest boxes are used by a range of native mammals. • The four most common occupants of nest boxes are, in descending order: the Common Brushtail Possum, the introduced Black Rat, the Yellow-footed Antechinus and the Common Ringtail Possum. • Several species of introduced mammals use nest boxes, but particularly the Black Rat during periodic irruptions of these pest rodents. This is in addition to other feral, hollow-using animals such as the Common Starling and the feral honeybee. • The use of nest boxes by different species is strongly associated with the characteristics of particular boxes, particularly the size of the entrance, the depth and volume of the box, and proximity to water. • The rate of use of nest boxes is typically greatest where natural hollows are most limited such as recently established plantings where all (or almost all) trees are small diameter stems that lack cavities. • The effectiveness of many nest boxes is significantly depleted by poor installation. This means that boxes are either unstable and rarely used or fall from trees soon after attachment. In both cases, effective occupancy time is greatly curtailed. The results from our various studies of nest boxes to date are preliminary and have yet to be published in the formal peer-reviewed scientific literature. However, our statistical analyses suggest that nest boxes have some value for some species of mammals, although it is unclear for how long and how often boxes will need to be replaced. In particular, it appears that nest boxes are likely to have greatest value in places such as plantings where natural hollows are rare or absent but the vegetation might provide suitable foraging habitat. It is also apparent that nest boxes can have some negative impacts such as the risk of promoting the spread of invasive ‘generalist’ species such as the Black Rat. Moreover, nest boxes will never adequately substitute for large old hollow-bearing trees. This is not only in terms of the array of types and sizes of cavities produced, but clearly also the mass flowering, mass seed production and large carbon storage roles played by large old hollow-bearing trees.

3 – M a mm a l s

67

Microbats are among the most abundant (but also most poorly known) mammals in woodlands. Work by other researchers suggest that individual animals can move very long distances in a night and between nest and roost sites (more than 14 km). Large paddock trees in particular appear to be disproportionately important foraging areas for microbats. Yet other research suggests that bats are important for controlling pest insects, with a given individual consuming more than half its bodyweight (or 3–10 g of insects) in just one night of foraging. (Pictured: (left) Gould’s Wattle Bat and (right) Chocolate Wattle Bat). Photos by Mason Crane.

What makes a good woodland remnant for arboreal marsupials? Most of our work on woodland remnants has focused on their value for birds and reptiles, with much less research on their use by native mammals such as arboreal marsupials. However, there are good data to suggest there are some features of woodland remnants likely to enhance their value for such animals as the Common Brushtail Possum and the Common Ringtail Possum. For example, the Common Ringtail Possum is more likely to occur in areas that support large logs (where they can shelter if tree hollows are unavailable) and where tree species such as White Box occur.2 The species is also likely to occur on farms with high levels of old growth woodland cover. The Common Brushtail Possum and the Common Ringtail Possum were both less likely to occur on farms with limited areas of plantings. The reasons for this result appear to be associated with the fact that farms with many plantings tend to be those where a substantial amount of past vegetation clearing has occurred and hence key structures such as large old hollow-bearing trees are uncommon or rare. This does not mean the establishment of plantings should be discouraged – in fact the opposite is the case.21 Rather, the results indicate that plantings do not provide readily substitutable habitat for old growth woodland for animals such as the Common Brushtail Possum and the Common Ringtail Possum.2 In these cases, it may take a prolonged period before areas that have recently been planted will eventually become suitable habitat, although providing nest boxes as a source of artificial cavities might have the potential to speed recolonisation for these species.

68

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Spotlighting is one of the traditional ways to survey for night-time animals on long-term monitoring sites with the temperate woodlands. A standardised approach to surveys must be used so that data from different sites and across many years can be readily compared. Therefore, a similar kind of equipment, rates of walking along a transect, and other protocols must be maintained to guarantee the quality of field data that are collected. Animals are identified from the body size and shape, call, and the colour of their eyeshine (the light that is reflected from the retina from beam of the spotlight). Photo by Luke O’Loughlin.

Mammals and travelling stock reserves Agricultural landscapes are comprised of land under different tenure. The network of travelling stock reserves is one of the kinds of land that has highly significant value for biodiversity, in part because they have been subject to less vegetation clearing and less intensive grazing pressure than elsewhere in agricultural landscapes. In Chapter 2, we discussed the values of travelling stock reserves for birds using scientific evidence obtained from repeated surveys in the Murray and Riverina regions of southern NSW. Our work also shows that travelling stock reserves are very important for native mammals, such as the Squirrel Glider, Sugar Glider, Common Brushtail Possum and Common Ringtail Possum. We found that travelling stock reserves supported significantly more arboreal marsupials than temperate woodland in private ownership. These effects were more pronounced in the Riverina region than the Murray.53 As in the case of birds, there are several reasons why travelling stock reserves are important places for biodiversity. For example, travelling stock reserves

3 – M a mm a l s

69

Radio-tracking individual animals is one of the few (and best known) ways of improving the understanding of how animals move within and between woodland patches. This information, in turn, helps guide the best ways to spatially arrange remnants and plantings to facilitate the movement of animals through farming landscapes. An extensive study by our ANU team entailed radio-tracking the Squirrel Glider in southern NSW. Animals first need to be captured before a small radio-transmitter can be attached to them. Many traps need to be fixed high in trees to capture a sufficient number of animals for the radio-tracking study to produce valid scientific information on the movement patterns of the Squirrel Glider. Photo still from Wildlife Friendly and Productive Farms, 2007.

typically support many large old hollow-bearing trees, which are critical nesting habitats for almost all species of arboreal marsupials – these animals cannot survive without access to these trees.48,49 Similarly, compared with woodland on private land, the understorey vegetation in travelling stock reserves is more likely to include plants such as wattles, which provide key food resources for animals such as the Squirrel Glider and the Sugar Glider. These results underscore why it is important to continue to maintain (and where possible further improve) the condition and ecological integrity of travelling stock reserves26 – a topic we revisit in the final section of this chapter. Another important role of travelling stock reserves is that they provide an interconnected set of reserves, thereby facilitating the movement of mammals and other kinds of animals throughout agricultural landscapes.

Can there be too many mouths to feed? Much has been written about the potential risks to biodiversity of intensive setstocking grazing by domestic livestock. This has underpinned recommendations to limit grazing pressure (including at certain times of the year, as adopted in the

70

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Australian Government’s Environmental Stewardship Program) to accommodate other values such as the maintenance of plant and animal biodiversity. But cows and sheep are not the only herbivores in agricultural ecosystems. This leads to the questions: • Can there be too many kangaroos? • What are the effects of high levels of grazing pressure by kangaroos on woodland biodiversity and vegetation condition? The answer to the first question is a definite yes! For some species, such as the Eastern Grey Kangaroo, the addition of numerous dams to the landscape, coupled with extensive vegetation clearing to establish pasturelands, has created the ideal combination of food and water resources to sustain major increases in populations. Moreover, natural predators such as the Thylacine and Dingo have been removed and traditional hunting by Aboriginal Australians has ceased. Together, these changes have resulted in species such as the Eastern Grey Kangaroo (and several other macropod species) being far more abundant than at the time of white settlement in Australia. As we discuss in greater detail in the chapter on invertebrates (see Chapter 5), over-abundant kangaroo populations can have significant negative impacts on groups of animals such as beetles54 and reptiles55. In the case of beetles, the species richness and abundance of predators, herbivores and detritivores all decreased significantly in areas subject to high levels of grazing pressure from large numbers of kangaroos (see Chapter 5). On the other hand, the diversity and abundance of almost all groups of beetles was significantly higher in areas subject to low levels of kangaroo grazing. The traditional way of tackling the problem of over-abundant kangaroos is culling – which is controversial among animal rights groups (who are not necessarily people with environmental or conservation concerns – see Box below).

Kangaroos and conservation – animal rights versus ecological science The management of natural resources is often characterised by a clash of conflicting values among people with markedly differing views on what they consider to be ‘right’. Ecologists generally consider that ecosystems should be managed in ways that conserve biodiversity. Sometimes this will involve controlling the potential impacts of practices designed to extract resources such as timber, wheat or wool. Animal rights groups have a different value set associated with protecting the rights and welfare of individual animals (typically charismatic species such as kangaroos). The impacts of protecting individual animals on the ecological integrity of the ecosystem in which those animals occur is often not part of the psyche of members of animal rights groups. News programs often portray animal rights groups as conservation groups. But they are not the same. This is because animal rights groups and conservation groups have markedly different value sets.

3 – M a mm a l s

71

Attaching a radio-transmitter to an animal is just the first step in gathering data on movement patterns. The next is repeated work with a radio receiver, both at night and during the day to provide information of where animals are feeding and the location of den trees during the day. As with almost all field-based scientific research, there are always surprises. In the case of the radio-tracking work on the Squirrel Glider, animals were found to make dramatic shifts in their movements during periods when trees were flowering, moving several kilometres in a night. Daytime tracking also revealed that gliders make dens in many different hollow-bearing trees, swapping frequently between them, possibly to avoid owls and other predators. Photo by Luke O’Loughlin.

Another, but more indirect, way of limiting the effects of over-grazing by kangaroos on groups of animals such as native invertebrates is to ensure that paddocks have areas of logs on the ground. Studies by Barton and colleagues showed that the negative effects of high levels of kangaroo grazing pressure were mitigated in areas where large numbers of logs have been added to patches of woodland.54

72

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Change in mammal abundance over time If (and how) populations of animals are changing over time is one of the most important, yet most difficult topics to investigate in ecology. It is critical to know if changes are occurring, such as whether there is a decline or increase in a population. However, it is also very difficult to gather good data on population change because it requires repeated surveys for many years, often at a large number of sites. Possums and gliders (arboreal marsupials) are widely considered to be among the groups of native animals most sensitive to human disturbance. On this basis, many land managers are keen to know answers to questions like: • •

Have populations of possums and gliders changed in agricultural landscapes over time? If so, are these changes linked to, for example, changes in the amount of woody vegetation cover? (As we have found for birds; see Chapter 2).

In recent research, we have begun exploring changes in the occurrence and abundance of the Common Brushtail Possum and the Common Ringtail Possum over the past decade or more. Our work has revealed that both species are being recorded on significantly more sites, and on more farms in 2014 than they were in 2002. Moreover, these positive changes in populations can be linked to an increase

The Squirrel Glider most often dens in large diameter trees in good condition. However, dead trees are sometimes also used. These trees are a target for removal by firewood collectors. In just 2 years of radio-tracking, 5% of the den trees occupied by the Squirrel Glider were cut down! Such rates of cutting will quickly exhaust numbers of these critical habitat resources for the Squirrel Glider and have significant negative effects on populations of the species. Photo by Mason Crane.

3 – M a mm a l s

73

How effective are nest boxes in promoting the recovery of hollow-dependent animals in restored areas? This sounds like a simple question, but it takes a lot of effort to obtain a convincing answer. We have considered this question as part of a major study of 150 nest boxes installed in 16 plantings and 14 woodland remnants. The main mammals using the nest boxes were the Common Brushtail Possum and the exotic pest, the Black Rat. Rarer species of conservation concern such as the Squirrel Glider did not use any of the boxes that were established, even though some of the boxes erected were specifically designed for the species. More work on the most effective design for these kinds of animals is needed. In the meantime, it is critical that populations of natural cavities in large old hollow-bearing trees are maintained and, if possible, increased. Nest box checking photo by Dan Florance, possums in a nest box photo by Mason Crane.

74

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Large old trees can support many different kinds of hollows of different sizes, shapes and internal volumes for many hundreds of years. Not so with a nest box. They are temporary and typically last for a handful of years; often much less than a decade. Our work suggests that nest boxes often had the shortest effective lifespan where they are most effective: where they are attached to young trees in plantings and in stands of young naturally regenerated woodland. This is because the increase in the diameter of the tree on which they are attached leads to the failure of fastening mechanism and the box falling to ground. It is clear that more research and engineering work needs to be done on nest box design to make them last longer. Photo by Mason Crane.

in the amount of woody vegetation cover on sites and on farms. This is an encouraging outcome because it indicates there are positive conservation outcomes from the considerable efforts to increase the amount of native vegetation cover in agricultural landscapes.

Mammals in woodland patches surrounded by pine stands In Chapter 2, we described the multi-faceted responses of birds inhabiting woodland patches where the surrounding landscape was being transformed from grazing paddocks to maturing stands of Radiata Pine. Birds are not the only animals in these landscapes, and we sought to find answers to such questions as: •

How have native mammals responded to an environment characterised by a mosaic of woodland patches and Radiata Pine plantations?

3 – M a mm a l s

75

Western society has a particularly psyche for ‘cleaning up’. This is often a good thing, but not always. Scattered fallen timber is a vitally important habitat for a wide range of plants and animals. These habitats are lost when the ground layer of woodlands is ‘tidied up’. Cleaning up the timber cleans away the wildlife! Detailed analysis of natural (unmanaged) woodland environments suggest that they would have typically supported up to 100 tonnes or more of fallen timber. After ‘cleaning up’, it can many decades, if not far longer, to recover appropriate volumes of fallen timber to support high-quality wildlife habitats. Photos by Damian Michael.

• Are changes in mammal populations linked with the maturation of plantation stands in the Nanangroe landscape? The answers to these questions are important given that the area of plantations continues to expand in Australia and elsewhere around the world. Indeed, more

76

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Lots of small mammals have disappeared from Australian landscapes due to habitat loss and predation by the feral cat and the Red Fox. Two small mammal species – the Fat-tailed Dunnart (top) and the Narrownosed Planigale (below) – still persist in the woodlands of south-eastern Australia, especially in areas where unimproved farming occurs and habitat is suitable. These mouse-like marsupials are members of the Family Dasyuridae: a group of carnivorous mammals that includes Quolls and the Tasmanian Devil. They are voracious predators of insects, frogs and small lizards and have even been known to prey on the introduced House Mouse. Both species like to shelter beneath fallen timber but they also shelter in narrow cracks of drying soil, a key habitat that is often destroyed by intensive farming practices. Photos by Damian Michael.

3 – M a mm a l s

77

than 5% of the world’s land surface – an area approaching the size of continental Australia – is presently in plantations, most of it conifer plantations. Our studies of mammal responses to Radiata Pine plantations are based on more than 16 years of repeated sampling in the Nanangroe region near Jugiong in southern NSW. During that time we have observed some important changes in mammal populations. These include: • The abundance of macropods such as the Eastern Grey Kangaroo, Black Wallaby (sometimes also called the Swamp Wallaby) and the Red-necked Wallaby have increased significantly over the past 14 years. • The abundance of the Common Wombat is significantly higher now than it was at the outset of the project in 1997. • Feral animals such as the Red Fox, European Rabbit, European Hare and the feral pig are increasingly common. • Arboreal marsupials such as the Common Ringtail Possum and the Common Brushtail Possum have varied markedly in abundance over time, especially in response to the drought periods in the mid-2000s. Overall, the numbers of possums and gliders in 2013 is similar to, or slightly higher than at the beginning of the research program in the late 1990s. Other species such as the Sugar Glider are now rarely observed, although they were never commonly recorded at any stage in the work at Nanangroe. Overall, it appears that most mammal species have been ‘winners’ from the establishment of plantations around the woodland remnants in the Nanangroe experiment. This result is in marked contrast to those from birds in which there were clear losers (the woodland and open-country species) and obvious winners (forest-associated species; see Chapter 2). There are several likely reasons for the positive changes in populations of most species of mammals. One of these is that,

The amazing sex life of the Yellow-footed Antechinus The Yellow-footed Antechinus is a 25–50 g micro-predator that is widespread but typically uncommon in many agricultural landscapes. The species belongs to a group of small carnivorous marsupials called Dasyurids. These animals are probably most famous among ecologists for their extraordinary mating system, which is like that of few other animals. Groups of males congregate inside a hollow tree and are visited by a female who selects a mate. This kind of bizarre behaviour in which a female comes to an area to select a mate is called lekking and, although it is common in birds, it is seen only in approximately a dozen species of mammal worldwide, primarily among ungulates but also in the marine mammal, the Dugong. Adult males of the Yellow-footed Antechinus invest almost everything in their one and only breeding season and die after an intensive mating frenzy and before their female mates give birth. This is thought to limit competition between males and females, especially during the critical period when females have dependent young.

78

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

(A)

(B)

(C)

The vegetation adjacent to country roads can be vital habitat (and sometimes the only habitat) for an array of native plants and animals. (A) The amount of clearing and intensive grazing along roadsides is often significantly less than elsewhere in agricultural landscapes. Some animals that use roadside vegetation are readily observed: the Sulphur-crested Cockatoo and the Australian Magpie are examples. Others are only very rarely seen. The Yellow-footed Antechinus is one such species. We have employed remote camera technology in field surveys of the Squirrel Glider (C) in roadsides and found that the Yellow-footed Antechinus was by far one of the most commonly recorded nocturnal animal. It is particularly attracted to bait stations filled with sardines and drizzled with honey (B). Drone image by Mason Crane, mammal photos taken by camera traps.

3 – M a mm a l s

79

There are three egg-laying mammals in the world: the Platypus, the Short-beaked Echidna and the now endangered Long-beaked Echidna that is restricted to New Guinea. The Short-beaked Echidna (or Echidna) occurs in almost every habitat in Australia, with the possible exception of very intensively managed farmland where no native vegetation cover remains and its key food resources of ants, termites, beetle larvae and other soil invertebrates are rare or very limited. The Echidna forms ‘mating trains’ when females are on heat when it can be common to see a line of animals. Photo by Dave Blair.

although the study area at Nanangroe continues to be grazed, there are now fewer livestock than before the commencement of the research, leaving more food for grazing and browsing animals such kangaroos, wallabies and wombats. There is also less feral animal control, with populations of the Red Fox and European Rabbit largely unchecked. Similarly, fewer kangaroos are now being shot compared with when the Nanangroe area was a grazing enterprise and populations of these animals were culled. Different factors likely account for the changes in populations of different arboreal marsupials. Both the Common Brushtail Possum and the Common Ringtail Possum are ‘generalist’ species that can eat the needles, bark and cones of Radiata Pine trees and hence the plantation may directly provide a new and additional food source for these animals. In addition, such treed environments may help promote the movement of these species through the landscape and limit their need to descend to the ground where they can be at increased risk of predation by feral animals such as the Red Fox.

80

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Large old trees are the largest and longest living organisms on Earth. They have many features such as large cavities, extensive lateral branches and deeply fissured bark that are critically important for many species. These features are not provided by smaller trees or artificial structures such as nest boxes, which are not used by many cavity-dependent animals (e.g. the Greater Glider). For example, large old trees provide critical denning and nesting habitat for more than 300 species of Australian cavity-using vertebrates. Large old trees take prolonged periods (often exceeding centuries) to develop their key attributes. Tracking the development, maturation, decay and collapse of large old trees is an important part of informed biodiversity conservation because these trees are so important for a very large number of species. Photo by Tabitha Boyer.

The challenge of the ‘Big 3’ – the Red Fox, the feral cat and the European Rabbit Co-abundance of exotic animals is a major problem for native mammal conservation. This problem is magnified in Australia – the continent where invasive animals have had the greatest impact. When large populations of rabbits occur in an area, large populations of cats and foxes also can be sustained. This has impacts on populations of native mammals, and is perhaps one of the reasons why so many Australian native mammals have suffered significant declines and/or extinctions. It is therefore important to coordinate the control of introduced species, so that feral predators and their exotic prey are both controlled.56

3 – M a mm a l s

81

Plantings are not often suitable habitats for many species of native mammals, particularly hollow-using ones. This is because the trees are not sufficiently large or old to develop cavities. One way to solve this problem is to establish plantings around large old paddock trees. This provides animals not only with nesting sites but also places to forage. In addition, the condition of paddock trees surrounded by plantings is typically better than isolated trees located in otherwise created (and often heavily grazed) paddocks. Photo by Damian Michael.

The ‘missing mammals’ – microbats More than a dozen species of microbats are known to occur in the grazing landscapes of south-eastern Australia. Several studies by other scientists have examined the foraging and roosting behaviour of microbats and, for example, highlighted the importance of large old paddock trees for these animals.57 To date, our research team has elected not to study bats in detail for several reasons. The primary one is that many species of microbats travel many kilometres between roost sites and where they feed, and this makes it difficult to determine what the detection of an animal means in an ecological context. That is, whether the individual is close to where it is nesting, where it is foraging, or on the long journey between the two. This, in turn, makes it difficult to make ecologically meaningful links between the location of records of a given animal and the characteristics of the locations where the detection was made. This is in marked contrast to, for example, detections of resident birds or most reptiles, for which the features of the area where an animal has been recorded such as vegetation type, tree height or the condition of the ground layer, is likely to reflect the suitability of habitat for that species.

82

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Our long-term field data show that the Swamp or Black Wallaby is an increasingly common sight in many farming landscapes in parts of southern Australia. The species responds strongly to increased numbers of plantings and overall native vegetation cover. Populations also increase in the absence of feral animals, particularly the Red Fox, which is a major predator. The Swamp Wallaby is a browser rather than a grazer and typically consumes small trees and shrubs rather than large quantities of grass and forbs. The species also eats underground fruiting fungi, sometimes better known as truffles. These fungi germinate after passing through the gut of the wallaby. The new developing fungi attach to the roots of trees and other plants and form a mutually beneficial or symbiotic relationship with them. The fungi is essential for plants because it takes up water and nutrients and transfers them to the host plant. The presence of these fungi is one of the reasons why eucalypts grow in the poor soils characteristic of many parts of Australia. They also protect the host plant from soil pathogens such as Cinnamon Fungus, which may cause dieback. In return, the truffles receive energy from the host in the form of carbohydrates. Retaining understorey vegetation and establishing plantings for the Swamp Wallaby will allow this complex animal–fungus–plant inter-relationship to prosper and benefit to vigour and growth of larger trees on a farm. Photo by Damian Michael.

Concluding comments The native mammal fauna of agricultural landscapes has been significantly depleted over the past 200 years. There are nevertheless many strategies that farmers and other land managers can employ to promote the conservation of native mammals on farms. In many cases these strategies will have only limited impacts on the economic viability of farm enterprises. In most situations, there will be strong consistencies between recommendations for farm birds and those for mammals – as we demonstrate in Chapter 7 on managing wildlife friendly farms.

3 – M a mm a l s

83

Kangaroos can be a common sight on many farms. Large populations of these animals can degrade the condition of woodlands and have negative effects on the habitat suitability for a range of other species such as beetles, reptiles and birds, as well as an array of native plants. Population management of kangaroos will often be required to maintain woodland condition and ensure ongoing habitat provision for other native animals. Kangaroo grazing pressure is reduced in woodland areas with scattered fallen timber and this is another reason to resist the temptation to clean up logs and branches in all parts of a farm (see photo on p. 75). Photo by Dave Blair.

This page intentionally left blank

‡7HQ&RPPLWPHQWVSSLQGG

$0

4 Reptiles

Australia is a global hotspot when it comes to reptile diversity. There are more reptile species in Australia than any other group of vertebrates, and new species are continuously being described every year. In 2000, 680 species of reptiles were formally recognised. By year 2014, this number had risen to 940 – an average of 20 new species per year. In our surveys of the past 17 years, we have recorded almost 80 reptile species, ranging from turtles and small skinks (sometimes also called ‘drop tails’) to venomous snakes. Most species we detect are skinks – lizards that belong to the Family Scincidae. This group is by far the most species rich group of lizards in Australia and they comprise almost 40% of the reptile fauna in our woodland studies. Two species in particular, Boulenger’s Skink and the Ragged Snake-eyed Skink, account for more than 80% of the total number of individuals we encounter. Our work on reptiles has been conducted at different spatial scales – from individual outcrops, to farms and across landscapes. But one important aspect of our research is to collect baseline data on the distribution and abundance of this poorly studied group. Unlike birds and mammals, there is very little historical data on the different types of reptiles that once lived in the landscapes in which we work. Therefore, it often difficult to determine whether populations of different species have declined, increased or remained stable over time. Only a handful of species such as the two mentioned above, as well as the Southern Marbled Gecko and the Eastern Brown Snake, could be considered common and widespread. Most species have limited or restricted geographical ranges. They

86

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Fig. 4.1.  Zoogeographic regions of Australia.

How are new species described? The description of new species can happen in two ways. First, advances in the techniques used in DNA analysis have enabled scientists to examine the relationships between different species and populations of the same species in greater detail than ever before. Phylogenetics is the branch of science that focuses on research that explores hereditary differences in DNA sequences. The end result is often the production of a phylogenetic or ‘family’ tree that either ‘splits’ a given species into two or more new species or ‘lumps’ two or more previous recognised species together on the basis of new information. In many cases, a single widespread species turns out to be two or more closely related, but distinct, species. Many of these new species are so similar in appearance that they cannot be identified solely on body shape or pattern. Instead, these ‘cryptic’ species can only be reliably identified based on geographical location or DNA analysis. In recent times, several well-known gecko species have been split into new species. Examples include the Leaf-tail Geckos in far north Queensland and Gehyra Geckos in the Pilbara region of Western Australia. Another way in which a new species is described is the old fashioned way. That is, a species unknown to science is discovered in a poorly studied environment such as the tropical rainforests of north Queensland. Today, species descriptions follow strict guidelines set out in the Code of Nomenclature, where species names are generally descriptive or acknowledge its place of discovery. However, it was once common practice for scientists to name new species after themselves or in honour of their colleagues.

4 – R e p t il e s

87

How are reptiles surveyed in agricultural landscapes? Many species of reptiles are cryptic animals that are hard to see and even more difficult (and sometimes extremely dangerous) to catch. We employ several methods to survey reptiles. The first is to set out artificial substrates under which reptiles will often shelter. We use three kinds of substrates – sheets of corrugated iron, sets of roofing tiles, and large wooden sleepers. These substrates roughly approximate the kinds of natural sheltering habitats used by different species of reptiles. Therefore, more species of reptiles will typically be recorded when a range of substrates is used than if only one of two are deployed.58 Our second method of surveying reptiles has been to conduct what is called a time-constrained active search. This involves systematically searching under logs, bark rocks and other substrates actively looking for different species of reptiles. Our time-constrained active searches take 30 min on each site. Almost 850 long-term sites in remnant woodlands and plantings have been systematically surveyed in this way over the past 5–17 years. A third method – the use of nest boxes – is primarily associated with detecting birds and mammals (although the most common inhabitant is an insect – the feral honeybee – see Chapter 5). However, reptiles such as the Lace Monitor and Southern Marbled Gecko occasionally use these artificial hollows. Finally, the eyeshine of reptiles such as geckos is sometimes detected during spotlighting surveys and the numbers of species of reptiles is routinely rerecorded as part of nocturnal research work.

are either cold-adapted (belonging to the Bassian zoogeographic region) and found closer to the Great Dividing Range (and high-elevation sites), or they are arid-adapted (belonging to the Eyrean zoogeographic region) and hence found in the western half of the region out on the plains (see Fig. 4.1). Most of the species we study have patchy geographical distributions. Some species may be naturally rare, due in part to their highly specialised habitat requirements. But it is without any doubt that many species have declined as a result of the widespread loss of critical habitat. In this chapter, we briefly describe some of the key findings of our work on reptiles.

A way of categorising reptiles Managing multiple species in agricultural landscapes is often difficult because there is no single land management solution that benefits all animals. Instead, conservation outcomes are often best tailored to meet the habitat requirements of broad suites of species. Groups of species that exploit a common resource, such as habitat and food, are called ecological guilds. These species can avoid direct competition by using the same resource at different times of the day. For example, many lizard species shelter beneath the flaky bark of large mature trees. Geckos, for instance, shelter beneath bark during the day and forage on tree trunks at night,

88

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Artificial substrates (also called cover boards or cover objects) are used to survey frogs, lizards, snakes and small mammals across our long-term research sites. Our data indicate that different species use the different types of substrates according to how they mimic natural habitat and the method of thermoregulation employed by a given species. For example, we have detected large numbers of the Tessellated Gecko sheltering within the bolt holes of the timber railway sleepers. In their natural habitat, this species shelters and raises its body temperature within tunnels constructed by trapdoor spiders and large crickets, after it has consumed them as prey. Small snakes such as the Curl Snake shelter in soil cracks and are often detected in the crevices of the timber railway sleepers; legless lizards tend to use roof tiles because they mimic surface rocks; and corrugated iron is used by a wide variety of species because its provides thermally suitable shelter. Using artificial substrates can be a cost-effective survey method and can be used on a long-term basis without destroying the natural environment. A huge amount of effort was required by our field staff to establish over 15 000 artificial substrates across all of our long-term woodland monitoring sites, which are inspected on an annual basis. Photos by Damian Michael.

4 – R e p t il e s

89

The Curl Snake is a small venomous elapid that is found in arid parts of eastern and central Australia, particularly in areas with cracking clay soils. It grows to an average length of 40 cm and may be encountered during the day sheltering in small numbers beneath fallen timber. Curl Snakes move around at night and actively search for prey such as geckos, skinks, legless lizards and small mammals. The species can be relatively common where suitable habitat exists, although it has declined in some areas due to the loss of ground cover. It is listed as a vulnerable species in Victoria. We have found a steady increase in the number of Curl Snakes using our artificial substrates in areas used for intensive grazing. We believe this is because the substrates we have deployed, such as railway sleepers, are providing critical key habitat in heavily grazed areas where ground cover is depleted. Railway sleepers also may help the species cope with localised flooding. During a survey of reptiles in the Murray catchment in 2010, we encountered a small group of Curl Snakes sequestered beneath our artificial substrates that were submerged under flood water. We observed this group over a 2-month period and they remained using the submerged substrates during the entire flooding period. It is possible that Curl Snakes have the ability of coordinated movement at very low body temperatures and they may even be capable of aquatic respiration whereby oxygen is absorbed from the water and transferred across the skin. Photo by Damian Michael.

whereas skinks that use the same habitat forage during the day and shelter beneath bark at night. Species that occupy similar places in the environment belong to the same habitat guild. We sought to classify reptiles based on their broad affiliations with habitat – that is, microhabitat guild membership (see Table 4.1). For every snake and lizard species we detected, we recorded the type of substrate it was using. We assigned each observation to one of seven microhabitat categories including: among grass, among leaf litter, basking on logs, basking on rock (or rocky outcrops), sheltering

90

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Rocky outcrops present themselves in many different forms, as pictured above. Rocky outcrops form from erosion over thousands of years, leaving behind a core of hard parent rock. Wind, water and sunlight interact to create rock outcrops with distinctive shapes. Outcrops comprised of granite are common in south-eastern Australia and provide habitat for a wide variety of rock-dwelling plants and animals. Granite outcrops are generally dome-shaped, have distinctive flared slopes, rise abruptly from the surrounding landscape and create stable micro-climates for plants and animals. Because of their island-like appearance, the geological term for dome-shaped rock formations is an inselberg, which literally means ‘island-mountain’. Geologists also have names for other types of outcrops, depending on the overall size and shape of the formation. The terms whaleback or turtleback are used to describe rock expanses that superficially look like the animal namesake. Other types of rock formations include castle koppie (an Afrikaans word for little head derived from the Dutch word kopje used to describe block-shaped outcrops) and nubbins (conical-shaped outcrops comprised of smaller rocks). Free-standing rock outcrops are often called tors and stand out like sentinels in agricultural landscapes. Photos by Damian Michael.

beneath logs, between flaky bark or beneath bush rock. We have recorded this information for more than 4000 individuals from over 50 reptile species. We found woodland reptiles can be assigned to six broad habitat guilds. These include species found primarily on large mature trees (arboreal), fallen timber (semi-arboreal) or rocky outcrops (saxicolous). Two more guilds shelter primarily beneath logs (fossorial) or beneath bush rock (cryptozoic). The last guild included species associated with terrestrial environments such as leaf litter, grasslands or areas of bare open ground. We found that 36% of all species were habitat specialists

4 – R e p t il e s

91

Table 4.1.  List of reptiles in agricultural landscapes based on microhabitat guild classification Habitat Guild

Niche

Species

Arboreal (species that shelter beneath flaky bark of large trees)

Generalist

Southern Marbled Gecko, Eastern Tree Dtella, Robust Velvet Gecko, Southern Spiny-tailed Gecko

Semi-arboreal (species that bask on fallen timber or tree trunks)

Specialist

Burns’ Dragon, Jacky Dragon

Generalist

Ragged Snake-eyed Skink, Elegant Snake-eyed Skink, Nobbi Dragon, Eastern Bearded Dragon, Lace Monitor

Saxicolous (species that live on rocky outcrops)

Specialist

Cunningham’s Skink

Generalist

Tree Skink

Fossorial (species that shelter in loose soil beneath large logs)

Specialist

Eastern Three-toed Earless Skink, Blackish Blind Snake, Eastern Blue-tongue

Generalist

Two-clawed Worm-skink, Bynoe’s Prickly Gecko, Timid Slider

Cryptozoic (species that burrow or shelter in loose soil beneath surface rock)

Specialist

Pink-tailed Worm Lizard, Copper-tailed Skink, Eastern Stone Gecko, South-eastern Slider, Brown-snouted Blind Snake, Thick-tailed Gecko

Generalist

Yellow-faced Whip Snake, Dwyer’s Snake, Red-bellied Black Snake, Olive Legless Lizard, Leaden Delma

Specialist

Common Dwarf Skink, Litter Skink

Generalist

Southern Rainbow Skink, Grass Skink, Garden Skink, Boulenger’s Skink, Shingleback, Eastern Brown Snake

Terrestrial (habitat generalists that use leaf litter, grass tussocks or open areas)

primarily associated with a single habitat such as bush rock or fallen timber. The nationally threatened Pink-tailed Worm Lizard is a good example of a reptile that specialises in sheltering beneath bush rock. Another important finding was that almost 80% of all species were associated with attributes of old growth remnant vegetation such as flaking bark of large mature trees and fallen timber, or non-renewable resources such as bush rock and rocky outcrops. Our findings have major implications for habitat management and reptile conservation. For many species, once their habitats are depleted or damaged, finding alternative habitat may not be feasible, unless the species is a habitat generalist capable of using other kinds of habitat. The implications are that if bush rock or fallen timber is widely collected from agricultural landscapes, reptile diversity can be dramatically reduced. It also means that once old growth habitat is degraded, it may take decades before new species are able to recolonise restored areas and, in the case of bush rock collection, species that rely on this resource may never fully recover. We will discuss the implication of this in more detail later in this chapter.

92

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Lace Monitor (or Tree Goanna) is the second largest lizard in Australia. Monitor lizards feed on a wide variety of live prey but they also feed on carrion. Because of this, they play an extremely important role in the environment by reducing the spread of disease and maintaining the health of ecosystems by preying on sick and injured animals and removing road kill. The Lace Monitor lays up to 14 eggs each year. These are usually laid in termite mounds located on the ground, but in the absence of terrestrial mounds, the Lace Monitor will lay eggs in active termite mounds in the hollow braches and cavities of large trees – a resource that is steadily disappearing from farming landscapes. The female excavates a hole in the termite mound, lays a clutch of eggs and then leaves the termites to reseal the eggs inside the nest. Interestingly, the female returns when the eggs are due to hatch and opens up the termite mound again to allow juvenile monitors to escape. Photo by Damian Michael.

Reptiles and regrowth woodland When agricultural land is abandoned, or when grazing pressure is reduced, native vegetation may start to recover through a process called passive regeneration or natural regrowth. Plant species that readily regenerate include Blakely’s Red Gum, many different wattle species, as well as other native plants such as teatrees and Cassinia. White Cypress Pine is another species that has the capacity to regenerate following soil disturbance and is often found in dense stands. Changes in agricultural land use practices over the last 50 years have enabled passive regeneration to become a widespread phenomenon. Our work on woodland birds (Chapter 2) clearly shows the importance of regrowth for improving bird diversity and conserving declining woodland birds. However, with several hundred stems

4 – R e p t il e s

93

Lizards in the Family Scincidae are among the most abundant vertebrates in most ecosystems in Australia, from alpine grasslands to desert dunes and tropical rainforests to the savannah woodlands. These lizards are called skinks and there are currently 438 described species in Australia. They range in size from 22 mm (snout to vent length) to over 30 cm and can be very difficult to identify without the aid of a hand lens and a technical dichotomous key – a tool that allows the user to determine the identity of a species by selecting one of a series of choices that leads to the correct name. Skinks are a fundamental component of the food web and are an important source of prey for other reptiles, native carnivorous marsupials and birds of prey. Because skinks can be very abundant, they play a key role in recycling nutrients and dispersing plant material. This collage shows nine of the most common skinks we have recorded across our monitoring sites. Top row left to right: Copper-tailed Skink, Eastern Three-toed Earless Skink, Tree Skink. Middle row left to right: Southern Rainbow Skink, Eastern Striped Skink, Ragged Snake-eyed Skink. Bottom row left to right: Boulenger’s Skink, Delicate Skink and Eastern Blue-tongue. Photos by Damian Michael.

per hectare (and sometimes several 1000 stems per hectare), stands of regrowth are usually dense shady environments. Presumably the suitability of this type of environment for some types of animals may be less than optimal.

94

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Many small snakes such as Dwyer’s Snake are active under cover during the cooler months of the year – a time when they can prey on dormant geckos and skinks that shelter beneath logs and rocks. Small snakes may live to up to 10 years and, like all species of snakes, they continue to grow throughout their entire lifespan. They also periodically shed their skin as they continue to grow. This process is called sloughing and occurs more often in young individuals and during times of rapid growth. A snake in the process of sloughing loses its shine and the eyes take on a ‘milky’ appearance, just like the individual pictured here. Sloughing can take several days and during this time snakes are vulnerable to predation and remain under cover until the new skin has formed and the old skin is ready to be shed. It is important to note that a shed snake skin can stretch up to 25% of the original length as it is pulled away from the body. When trying to determine the true length of a snake from its slough, it is important to take into account the ‘stretch factor’. Photo by Damian Michael.

Given reptiles are ectothermic organisms (i.e. they regulate their body temperature by exchanging heat with their surroundings), we postulated that stands of natural regrowth may not be suitable habitat for sun-loving reptiles. Conversely, we also postulated that shade-tolerant species may benefit from the increased shade levels that result from dense regrowth and canopy closure. We sought to test these assumptions by examining the response of reptiles to different vegetation types and different vegetation structural growth forms in the South West Slopes bioregion. To complete this work, we selected 165 sites in three different vegetation communities: (1) Western slopes grassy woodland dominated by White Box; (2) riparian woodland dominated by River Red Gum; and (3) Upper Riverina dry sclerophyll forest dominated by Red Stringybark. We further classified each site according to its growth form – old growth or regrowth (we did not distinguish between coppice regrowth and seedling regrowth). We gathered presence/absence data on reptiles at each site using active searches and inspection of artificial substrates on four repeat occasions between 2002 and 2008 (see Box on

4 – R e p t il e s

95

The Eastern Brown Snake is considered to be the world’s second most venomous terrestrial snake based on a ranking method derived from the amount of venom required to kill half of a population of mice in a laboratory setting (a figure known as the lethal dose, 50% or LD50). The species is also responsible for a large number of snake-bite-related hospitalisations. Avoiding unnecessary interactions with this species, and snakes in general, is well advised. This is especially important because identifying snakes based purely on colour and pattern is unreliable. The Eastern Brown Snake is extremely variable in colour, ranging from various shades of brown, through to grey, orange, yellow and even black. Some individuals have dark markings over the body and some individuals may be completely banded. Juvenile Eastern Brown Snakes usually have black heads and black napes and they too may be banded. The collage above shows the various colour and pattern morphs of the species. Just as body colour varies, so too does the properties of their venom. The proteins in the venom produced by juvenile snakes can often be very different from the proteins found in the venom of adult snakes of the same species. Venom components may also vary within populations of the same species. Such variation is believed to be a result of differences in prey availability over a species’ entire range. The toxins required to subdue a harmless lizard are very different from the toxins required to subdue a rodent, which could easily injure or kill a snake. Composite shades of Brown Snakes montage by Bryan Robinson, juvenile photo by Mason Crane.

96

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

p. 87). This amount of survey effort yielded 25 reptile species and over 2200 individual animals.59 We found clear differences in the number of species between vegetation types and also between vegetation growth forms. White Box sites and Red Stringybark sites supported 19 and 18 species, respectively, compared with just seven species in the River Red Gum sites. We also found strong differences in the number of species between growth forms. However, our results were not consistent among all vegetation communities. For example, we recorded fewer species in woodland regrowth compared with woodland old growth but we recorded more species in forest regrowth than forest old growth. When we examined the attributes of our sites in more detail, we found that the presence of bush rock or rocky outcrops (mostly granite) contributed significantly to the number of species found at a site.

Many non-venomous and completely harmless lizards have the unfortunate trait of looking superficially like snakes. Just because a reptile has an elongated body and appears to lack obvious limbs does not make the animal a snake. In Australia, there are more than 40 species of legless lizards placed in the Family Pygopodidae (meaning flap-footed). This group of lizards are closely related to geckos and differ from snakes in several key ways. Apart from having separate evolutionary lineages, legless lizards possess obvious ear openings, have small hind-limb flaps, and have broad fleshy tongues and extremely long tails (which are easily broken) relative to the length of their body. By contrast, snakes do not have ears, entirely lack limbs (with the exception of pythons which have small spurs), have forked tongues, and have short tails relative to the length of the body. Legless lizards also have the ability to vocalise and will make a squeaking sound when they are excited or upset. Our long-term research has found that the Olive Legless Lizard is quite common in native pasture and will also colonise tree plantings, especially plantings where intense grazing is excluded and which support tussock-forming grasses. Photo by Damian Michael.

4 – R e p t il e s

97

Boulenger’s Skink is the most common lizard found across our long-term monitoring sites and can be found in a broad range of habitat including heavily disturbed farmland as well as urban areas. In many cases, more than 50% of all individuals we record at a site and within a study area are this one species. Other studies have found it can reach densities as high as 1000 individuals per hectare in suitable habitat. During the breeding season, male Boulenger’s Skinks develop a bright orange flush to the chin and neck. Species that change colour during the breeding are said to be sexually dichromatic and this is believed to be an important feature for attracting potential mates. Many species of lizards are also sexually dimorphic, whereby females have longer bodies to accommodate developing embryos and males have large heads, particularly in species that engage in combat and fight rival males to win access to females. Photo by Damian Michael.

Previously in this chapter we discussed the different guilds associated with rocky outcrops and bush rock – the saxicolous and cryptozoic guilds. Not surprisingly, the presence of rocks in the landscape means that additional species may be present.

Do reptiles use tree plantings? In Chapter 2, we discussed the value of restored areas for woodland birds. We extended the work on plantings to other groups such as reptiles by asking the questions: • •

How valuable are tree plantings for reptiles? Which species use such areas and what attributes of planting influence their use by reptiles?

To determine what reptile species use tree plantings, we have studied more than 60 plantings on the South West Slopes of NSW over the past decade. In the

98

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Southern Rainbow Skink is another lizard that is sexually dichromatic, whereby males (left) develop bright colours along their flanks during the breeding season. This species belongs to a group of lizards that move their tails from side to side and up and down while foraging for prey. This behaviour is called caudal luring and is used by many species of snake, including the Common Death Adder, to attract prey. In lizards, this behaviour is believed to serve as a distraction to potential predators. It is not uncommon to find this species missing part or all of its tail. Studies have found that skinks that lack tails leading up to the breeding season are less likely to breed. Photos by Damian Michael.

Many lizards will readily drop their tails if they feel threatened or are being attacked by a predator – a defensive mechanism found in a wide range of species and called caudal autonomy. Losing a tail, but surviving an attack is always the best outcome. However, losing a tail also comes at a cost to the lizard. For example, individuals that have recently lost their tails may find it more difficult to move through the environment and subsequently they can become an easy target for predators in the future. Furthermore, species such as the Southern Marbled Gecko store important fats in their tails, which are used in reproduction and surviving long periods of inactivity during the winter months. It may take several months before the tail fully regenerates and the new tail usually is a different colour and shape from the original. Photo by Damian Michael.

4 – R e p t il e s

99

The Pink-tailed Worm Lizard is an Endangered species of legless lizard that is found in small isolated populations in areas of grassy woodland between Gunnedah in NSW, throughout the ACT and as far south as Bendigo in Victoria. The species is very cryptic and is generally found sheltering beneath shallowly embedded surface rocks, where it occupies the brood chambers and tunnels of various ant species, the larvae and eggs of which it eats. The Pink-tailed Worm Lizard is closely related to geckos and accordingly, it is active on the surface at night during warm weather. Although this species is relatively small, growing to a length of 14 cm (measured from the snout to the vent), it is capable of moving several hundred metres away from suitable rock cover. However, the species generally occupies a very small home range and will often use the same rock or group of rocks throughout the year. Over the past 10 years, we have recorded this species beneath artificial substrates, which suggests that critical habitat for this species can be enriched by placing roof tiles or artificial rocks in areas where the species occurs and the habitat has been lost or degraded. Over the past 5 years surveys by the ANU team have more than doubled the number of records of this rare lizard in NSW. This highlights how important it is to maintain long-term research to collect important information on rare and endangered species. Photo by Damian Michael.

same way that we survey reptiles across all of our studies, we established arrays of different artificial refuges (see Box on p. 87) and complemented this method with active searches of natural habitat. Given the young age of most of the tree plantings that we surveyed (less than 30 years old), we did not expect to find many tree-dwelling species. Instead, we predicted that tree plantings would support only widespread habitat generalist species; that is, snake and lizard species capable of living in paddocks and moving through the landscape, such as Boulenger’s Skink. However, our results were surprising. Boulenger’s Skink was one of the most commonly detected species, along with the leaf litter generalist the Southern Rainbow Skink. But we also found

100

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

reasonably large numbers of the Southern Marbled Gecko. This species shelters beneath the bark of large mature eucalypt trees and is the species most commonly encountered catching insects on the walls of buildings during hot summer nights. In our planting study, we detected the Southern Marbled Gecko between sheets of tin that we use as a survey method. These artificial refuges emulate habitat and temperature conditions similar to the natural habitat of some arboreal species. But where did these geckos come from? They were unlikely to have been living in the paddock before the tree plantings had been established, or were they? The answer is yes. They do live in paddocks, but not on the ground. They use isolated or scattered paddock trees – large mature eucalypts several hundreds of years old that are the living legacies of a once widespread woodland community. It

Our long-term studies show that only a small number of reptile species use tree plantings. Generally, the kinds of species that use tree plantings are those that live in native pasture or are habitat generalists capable of moving through open farmland. Tree plantings can, however, be designed to increase the habitat suitability for reptiles. Trees and shrubs can be planted 5–10 m apart to allow the sunlight to reach the ground; fallen timber can be added to the planting to provide shelter and foraging areas; large mature trees, dead trees and small wetlands can be incorporated into the planting to provide habitat for arboreal species and frogs (which can be prey for some species of reptiles). Grazing can also be used as a tool to reduce the biomass of grass. Plantings that are dominated by exotic grasses will often support fewer species of reptile than tree plantings that have a ground cover of native grasses. Our research also indicates that tree plantings that contain bush rock also support more species of reptiles. Photo by Damian Michael.

4 – R e p t il e s

101

Remnant vegetation is the single most important type of habitat used by reptiles on a farm. A good quality remnant will generally support a wide variety of microhabitats, including large trees with flaky bark, fallen timber, surface rocks, mats of leaf litter, tussock grass and patches of lichen encrusted soil. High-quality remnant vegetation is extremely rare across our study area and generally the only places it occurs are in areas that have never been logged, heavily grazed, cropped or fertilised. The more microhabitats that are available in the remnant, the more species of reptiles that are likely to occur. In a recent study, we found that more than 80% of the reptiles that occur on our monitoring sites across the entire Box Gum Grassy Woodland ecosystem strongly depend on old growth elements such as large old eucalypt trees and fallen timber, as well as structurally complex rocky outcrops. These types of habitats are incrementally being lost across the landscapes and, in the case of large old trees, may take several hundred years before they are replaced. Photo by Damian Michael.

is from these important landscape features that geckos are able to disperse and colonise restored areas. If they are lucky enough to encounter our sheets of tin, then they generally stay put, and breed successfully. Indeed, it is not uncommon for us to find half a dozen individuals living between the sheets. Another reptile common in tree plantings was the Olive Legless Lizard. This species is steel-grey to olive-green in colour with a yellow tinge to its throat and neck. It grows to over 30 cm in total length, although two thirds of its length is tail. This species is quite common in grasslands and its elongated body is a perfect adaptation for ‘swimming’ through tussock grasses. We found that the Olive Legless Lizard was more likely to use restored areas that are excluded from grazing.

102

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Plantings that are not grazed have more grass cover and also contain larger clumps of the exotic perennial Canary Grass, a species that has a similar tussock structure as native perennials such as Kangaroo Grass. When tree plantings mature, in many cases grazing is reintroduced with often predictable outcomes – heavily grazed tree plantings tend to support very few lizard species. Another key aspect of tree plantings that determines what types of reptiles use them is the presence of bush rock. We have previously discussed the benefits that rock cover can provide by increasing the number of reptile species in a given area. We found a similar pattern in tree plantings. If rocks were present, then we were more likely to detect rock-dwelling species. For example, in 2010, we recorded the threatened Pink-tailed Worm Lizard using slate rocks located in a large tree

Nest boxes are widely used as a management tool to restore habitat for hollow-dependant wildlife. Different box designs are used to attract different species and projects can be developed to target threatened species such as the Squirrel Glider. A small entrance is often enough to prevent unwanted species such as the Common Brush-tailed Possum from taking up residence. However, occasionally, we find animals using boxes that were design for other species. This photo shows a juvenile Lace Monitor using a box that was designed for the Squirrel Glider. Lace Monitors are also hollow-dependant and studies have found they occupy overlapping home ranges up to 150 hectares in size. Within this range they require access to a large number of shelter sites: mostly hollow branches but also large hollow logs and animal burrows. Lace Monitors have declined in many parts of their range and in Victoria the species is included in the advisory list of threatened fauna. Photo by Damian Michael.

4 – R e p t il e s

103

There are ~100 species of front-fanged (elapid) snakes in Australia. Most are small, grow to less than 50 cm in total length, and their venom is not considered lethal to humans, although a bite from large specimens can be extremely painful. Many small snake species are brown in colour and are mistaken for the Eastern Brown Snake and unnecessarily killed. The snakes featured in this collage include six of species that are found in the Box Gum Grassy Woodlands of south-eastern Australia. Clockwise from the top left: Eastern Bandy Bandy, Little Whip Snake, Dwyer’s Snake, Yellow-faced Whip Snake, Curl Snake and Red-naped Snake. The Bandy Bandy spends most of its time buried beneath rotting logs, surface rocks and in loose soil. Following rain on humid summer nights this species may be encountered on the surface searching for Blind Snakes, a prey item on which it exclusively feeds. Most other snakes prey on frogs, small lizards and occasionally small mammals. Many of these small snakes have declined due to loss of fallen timber, bush rock removal, and groundcover degradation. However, our research is finding that some populations of small snake species are increasing in number in areas that have been fenced off from stock and the grazing regime has changed from continuously grazed to only being grazed in the winter months. Photos by Damian Michael.

planting near Howlong.59 This species was likely to have been present at the site before the plantings were established, which raises several important questions when it comes to establishing a planting in and around rocky areas.

104

•

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

How dense should the plantings be, what plant species should be used and what plantings methods are most appropriate so as not to disturb surface rocks and the resident lizards using them as shelter?

Findings from a study that focused on reptile diversity and granite outcrops found lizard numbers were significantly lower on rocky outcrops that were heavily shaded by regrowth vegetation as opposed to outcrops that supported widely spaced old growth trees and low growing shrubs.44 This result has important implications for revegetation around rocky outcrops and on hilltop areas with lots of bush rock. We suggest that it will be extremely important to carefully consider tree density, plant selection and the spacing of plants to avoid any potentially negative effects that may result from increased canopy cover and associated amounts of shade.

Boulenger’s Skink and lizard morphology Boulenger’s Skink is one of the most common lizard species in our study area. Therefore, in 2008, we designed a study in the Riverina and South West Slopes bioregions to answer a widely debated global question: •

Do reptiles conform to Bergmann’s rule?

Colour is often an unreliable feature in which to identify snakes; although it can be useful, many snakes cannot be identified based on colour alone. This image of a ‘dark brown’ coloured snake is actually a Spotted Black Snake (also called a Blue-bellied Black Snake in southern parts of its range). It is a member of a group of snakes that includes the King Brown or Mulga Snake. The venom of Black Snakes is extremely toxic and consists of myotoxins and necrotoxins that damage muscle and cause tissue death. A bite from these species could be lethal, although there has not been a reported death from a Black Snake for over 50 years. By contrast, Brown Snake venom consists of powerful neurotoxins that cause paralysis and interfere with the nervous system. Photos by Damian Michael.

4 – R e p t il e s

105

How are lizards measured? Measuring snakes and lizards in the field is difficult and requires patience and practice. This is because most species tend to squirm out of your hands. Snakes, in particular, are rarely still. One of the most common measurements that researchers collect is the snout to vent length or SVL for short. The SVL is measured from the tip of the nose to the ventral scale (the region where the body ends and the tail begins). Digital callipers are used to measure small lizards and soft tapes are used to measure snakes. However, when handling venomous snakes, we need to wear thick leather gloves, hold the snake gently by the neck and run the tape down the length of the body. Data on tail length also are collected but because many lizards are prone to dropping their tail when threatened, SVL is a more reliable estimate of body size. In morphology studies, many other measurements are collected including head length, head width, limb length and scale counts, particularly the number of scales along the belly and around the body. Sometimes, differences in these attributes are enough to alert scientists to a new species. In other instances, counting body scales is the only reliable method for identifying species of animals such as Blind Snakes.

Bergmann’s rule states that warm-blooded animals that live in cold climates tend to be larger than similar species in warmer environments. This rule was originally formulated to help explain differences in the body size of different species across large latitudinal gradients, generally at continental scales. Many studies have since applied the rule to populations of the same species. However, most studies on reptiles have found that snakes and lizards don’t follow Bergmann’s rule and are instead smaller in colder environments. But the evidence isn’t conclusive and warrants further investigation. We decided to test this hypothesis by examining body size in Boulenger’s Skink across a gradient in elevation and temperature. We measured, weighed and determined the sex of over 300 skinks across our sites in southern NSW (see Box above for how to measure lizards). We also took a small tail clip for use in DNA analysis (see Box on p. 86) just in case we were dealing with any undescribed species that could potentially influence our results. We then collected a broad range of variables that we thought might possibly influence body size, including: elevation, temperature and rainfall data; habitat attributes such as vegetation type and amount of fallen timber; and land use information such as the grazing regime at each site. We then used statistical methods to explore the relationships between body size and the selected variables. The first pattern that emerged from these data was that female skinks were significantly larger and heavier than male skinks – a phenomenon known as sexual size dimorphism (where one sex is larger than the other). In species that are

106

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

territorial and engage in ritual combat, males tend to be the larger sex. When females are the larger sex, this is often attributed to embryo development. Because Boulenger’s Skink lays eggs, larger abdomen size appears to have been selected to allow for the development of up to four eggs in a single clutch. The second pattern that emerged was that skinks in the South West Slopes were, on average, larger than skinks in the Riverina. These differences were attributed to regional differences in temperature and rainfall. So, it would appear that in some cases, reptiles can grow larger in cooler environments; although we can’t rule out the possibility that other underlying reasons such as prey availability may also contribute to regional differences in body size.

Rocky outcrops and reptiles Rocky outcrops are found across Australia and occur in a broad range of vegetation types. They range in size from large sandstone escarpments along the east coast of Australia to small intrusive islands of rock embedded in agricultural landscapes. Outcrops of granite, or inselbergs as they are commonly called, are common in our study areas. They vary in size and shape and include formations such as large domed-shaped hills (bornhardts), boulder-strewn conical outcrops (nubbins) and block-shaped intrusions (castle koppies or kopjes). Dome-shaped bornhardts are especially common in Western Australia and South Australia’s granite country. Here inselbergs such as Pildappa Rock, Mount Wudinna and Murphy’s Haystacks rise above the flat plains. Granite intrusions also are found throughout the Great Dividing Range from central Victoria to far north Queensland, and include Bald Rock near the Queensland-NSW border, one of Australia’s largest exposed granite surfaces. Smaller inselbergs such as castle koppies are common in southern NSW and conical-shaped nubbins are found throughout the Northern Territory. A key feature of granite inselbergs is their isolation. In this, they are akin to oceanic islands and, like island habitats, their insularity makes them vulnerable to human land use practices. Granite rocks are prized for buildings and gardens, and some outcrops bear the scars of quarrying or recreational activities such as rock crawling (or rock-hopping), an extreme off-road motor sport gaining popularity in Australia, in which specially designed dune buggies are craned on top of outcrops, and drivers scale large boulders and rock piles. Many inselbergs also occur on prime agricultural land, where their ecological integrity has been compromised by clearing of the surrounding land, weed invasion, intensive grazing by livestock and/ feral animals, altered fire regimes and, in some places, defoliation of lichen by the introduced Portuguese Millipede. Although many rocky outcrops in farming landscapes are cleared of vegetation, they are important for a large number of reptile species that use hot exposed surfaces. The rocky outcrop community includes species such as the Tree Crevice

4 – R e p t il e s

107

The Eastern Bearded Dragon is one of 81 species of lizards in the Family Agamidae. These lizards have one of the highest preferred body temperatures of any reptile in Australia and are often seen basking on roads during the warmer months of the year. They can be relatively common in areas where there is abundant fallen timber, but the species also will readily use human infrastructure such as fence posts and gates on which to perch. Perching behaviour is a characteristic trait of many dragon species and is used to maintain a stable body temperate (usually between 35–39°C), visually scan the ground for passing prey, and also to keep an eye out for rival males. Many dragons including Eastern Bearded Dragons wave their arms in a circular motion when in the presence of other dragons of the same species or when approached by a larger individual. Some species also use head bobbing as a sign of dominance: a behaviour often seen during the breeding season. Rapid head bobbing is usually associated with territorial behaviour, whereas slow head bobbing can be a sign of submissive behaviour. Dragon populations have declined in many areas largely due to loss of ground cover habitat and nest predation by the Red Fox. Photo by Chris MacGregor.

108

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Skink, Southern Marbled Gecko, Eastern Tree Dtella, Ragged Snake-eyed Skink, Copper-tailed Skink, Cunningham’s Skink and the Inland Carpet Python. We explored the biodiversity values of rocky outcrops in more detail and investigated a widely applied theory in ecology – the theory of island biogeography. This theory proposes that the number of species on an island reflects a balance between the rate at which new species colonise and the rate at which established species go extinct. Larger islands are expected to have more species than smaller ones and structurally variable islands are predicted to support more species than those with homogenous habitat. We tested these assumptions by studying 50 granite inselbergs in the South West Slopes bioregion and used reptiles as the target group to study. True to our predictions, larger inselbergs supported more reptile species than small ones, and reptile richness increased relative to outcrop complexity. Reptile diversity also varied with inselberg type – nubbins, which are characterised by small conical boulder piles, mostly supported ground-dwelling lizards, whereas castle koppies, with large boulder stacks and numerous horizontal crevices, supported saxicolous (rock-dwelling) species.44 We also found that paddock management had a significant effect on the number of reptile species that inhabit rocky outcrops. Inselbergs in heavily cleared landscapes had fewer reptiles than inselbergs surrounded by native vegetation, native pasture and paddock trees. These findings suggest that maintaining viable reptile populations on rocky outcrops will be significantly influenced by the management of adjacent paddocks.44 Many reptiles disperse from small outcrops to find mates and avoid inbreeding. Therefore, suitable habitats such as logs, native grass and paddock trees in the landscape will facilitate the movement of reptiles around agricultural landscapes. We found strong evidence that the habitat surrounding a rocky outcrop is important for maintaining populations of the Tree Crevice Skink. This species of social lizard forms nuclear family groups comprising a breeding pair and several generations of their offspring. In heavily cleared landscapes, the Tree Crevice Skink (contrary to its name) may be the only lizard species living on isolated rock outcrops, even those surrounded by a monoculture of crops. Given this, we sought to answer the question: • How does the Tree Crevice Skink survive on rocky islands in paddocks surrounded by environments such as canola crops? The answer is probably associated with the longevity and close-knit social system of the Tree Crevice Skink. Tree skinks can live more than 20 years, which means they have many opportunities for dispersal once crops have been harvested or paddocks are left fallow. Large populations of the Tree Crevice Skink can be found on structurally complex inselbergs, such as castle koppies. Larger family groups dominate the highest and biggest rocks, and non-breeding males tend to ‘float’ in the

4 – R e p t il e s

109

peripheral zone, waiting for their chance to join another family group or disperse to other suitable habitat,60 and thereby maintain gene flow between outcrops.

Management interventions and reptiles Reptile populations around the world have been declining since the 1970s. In Australia, habitat fragmentation and agricultural intensification has been one of the major causes of reptile decline. So what is being done to reverse this situation? Agri-environment schemes (AES) may be one solution. AES involve paying farmers to modify farming practices with the goal of providing environmental benefits such as increased biodiversity. The types of incentives that landholders are trialling vary from site to site and region to region but generally include: (1) reducing grazing pressure by limiting the number of stock or altering the intensity and timing of grazing; (2) actively controlling weeds and pest animals; (3) halting or reducing levels of firewood and bush rock removal; and (4) actively restoring areas of native vegetation by replanting (enhancement plantings). Some of our previous work has shown that these initiatives can improve woodland bird diversity (see Chapter 2). An important question is: •

How effective are these types of environmental works for improving reptile diversity?

We examined this issue in a study in the western Murray region of southern NSW where a conservation incentive scheme had been implemented as part of efforts to improve environmental conditions on farms. The incentive scheme provided landholders with funds to fence remnant vegetation and control the intensity of grazing by domestic livestock. Our study involved contrasting the vegetation and associated biodiversity on four kinds of sites: those where the incentive scheme had just been implemented; those where the incentive scheme had been in place for several years; those where there was no incentive scheme (i.e. set stocking grazing with a sole production focus); and travelling stock reserves, which act as a kind of best condition benchmark because grazing pressure has been generally limited in these places for many decades (and possibly much longer). We recorded a total of 31 frog and reptile species, but again, like in many of our studies, Boulenger’s Skink and the Ragged Snake-eyed Skink accounted for almost 80% of all individuals recorded. When we examined differences in the number of reptile species among the four management types, we were surprised to find very little difference in species richness between production areas and sites that had been fenced off from livestock or travelling stock reserves.61 Does this mean that environmental interventions are not particularly effective for reptiles, and are we simply wasting our time trying to protect this group of animals? Not at all! When we looked at differences in the number of individuals (species

110

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

abundance), we found that travelling stock reserves and fenced-off remnants supported more individual lizards, even though they were mostly the common species. More lizards in an area means more food for predators, including other reptiles such as Burton’s Legless Lizard, small snakes, raptors and even the threatened Bush Stone-curlew. We suggest it may take more than 10 years for most reptiles to respond to remnant management, primarily because most lizards are small and many have poor dispersal ability. In which case, altered management regimes will be needed over a prolonged period to ensure the full benefits for reptiles are realised.

Reptile assemblages A key topic in ecology is the concept of community assemblages. Put simply, assemblages are associations of populations of two or more different species that occupy the same geographical area or habitat. We have previously discussed the rocky outcrop reptile community – a group of reptiles that are more commonly found on granite outcrops than in remnant vegetation. But different community assemblages are also associated with different vegetation types. We examined reptile assemblage structure in the western Murray region of southern NSW and found communities differed significantly among structurally different vegetation types.61 In Boree woodland – a vegetation type dominated by a medium-sized wattle tree (Weeping Myall) and an understorey of Spiny Saltbush – the key species that defined this community were the Samphire Skink, Tessellated Gecko and the Shingleback. By contrast, species that were associated with Sandhill Woodland – a vegetation type dominated by White Cypress Pine and a wide variety of shrubs – included the Southern Spiny-tailed Gecko, Timid Slider, Eastern Tree Dtella and Dwyer’s Snake. Black Box and Grey Box Woodland shared a very similar reptile community that included species such as the Lace Monitor, Southern Marbled Gecko and Eastern Bearded Dragon – species dependent on large hollow-bearing trees and fallen timber. Clearly, different reptile communities are associated with different vegetation types. However, even though reptile assemblages are well structured, not all sites support all species – many sites have a subset of the actual community, which suggests that some species have become locally extinct, or other factors, such as long-term evolutionary process, are at play in structuring reptile communities. This is a really important concept when it comes to conservation planning because it means that planning will have to be applied at multiple spatial scales. For example, excluding livestock grazing from one patch of Sandhill Woodland may increase the abundance of the Timid Slider (a fossorial species that ‘swims’ through sandy soil). However, to improve overall reptile diversity (the number and abundance of species), Sandhill Woodland may need to be linked with other patches of Sandhill

4 – R e p t il e s

111

Carpet Pythons One of Australia’s most iconic python species is the Carpet Python, which comprises several subspecies found throughout all mainland States and Territories. Carpet Pythons are not venomous. Many people keep them as pets, although they are more than capable of inflicting a painful bite. The subspecies that we occasionally encounter in our woodland studies is the Inland Carpet Python (commonly known as the Murray–Darling Carpet Python). This python is silverygrey in colour with dark blotches along the body. It can grow to over 3 m in length, although the average size is around 2 m. It is semi-arboreal but also inhabits rocky outcrops, farm sheds and rural buildings. Anecdotal evidence suggests that the Inland Carpet Python has declined in parts of its range. We therefore decided to evaluate its rarity in more detail by asking long-term landholders in north-eastern Victoria63 and the South West Slopes of NSW64 if they had ever encountered this species and, if so, where and when? One theme that emerged from the study was that pythons were relatively common in rural areas up until the time when myxomatosis was introduced to Australia in 1950 to control rabbits. Since the 1950s (and even as late as the 1960s), populations of the Inland Carpet Python steadily declined primarily because rabbits, which constitute a large proportion of their diet, also declined. Where pythons once preyed on small to medium-sized native mammals including bettongs, bandicoots, stick-nest rats and other native rodents, nowadays introduced mammals fulfil this role. Our surveys also indicated that python populations are primarily associated with rocky outcrops (places that provide thermally suitable hibernation sites) and areas where rabbit numbers are still plentiful. In many cases, granite outcrops occur as isolated habitat islands surrounded by grazing or cropping land. This raises some important issues about how to best control rabbit numbers in and around rocky outcrops. This is because: (1) pythons rely on rabbits as a high-energy food source; and (2) pythons shelter in rabbit burrows during the spring and summer months. To avoid accidental mortality of pythons, we suggest that rabbit warrens are ripped during the cooler months when pythons are more likely to be hibernating in tree hollows or deep within rocky crevices. However, before rabbit numbers are controlled, it is necessary to ensure that pythons have an alternative food source available, whether it is arboreal marsupials such as the Common Ringtail Possum or nesting birds. To achieve this, we recommend that the native vegetation surrounding rocky outcrops is enlarged and wildlife corridors are created to link up with other remnant vegetation in the landscape with the aim of increasing prey diversity.

Woodland by establishing intervening vegetation types such as Boree or Black Box. These intervening vegetation types may not be the preferred habitat for Sandhill Woodland species such as the Timid Slider, but this species (and many others like it), temporarily frequent other vegetation types by using particular habitat elements such as the build-up of soil around fallen timber. The ability of many species to use

112

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Carpet Pythons (or Carpet Snakes) include some of Australia’s largest snakes that can be found in farming landscapes. The name derives from the body pattern of some specimens, which resembles the pattern of old-fashioned carpets. Studies that have examined the prey items of pythons found that the introduced House Mouse, Black Rat and European Rabbit are common prey, along with various species of native marsupials and birds. The pest control service that pythons provide was once well recognised by landholders. In fact, it was once a common practice for farmers to relocate pythons found on their properties or sourced from other areas to hay sheds to control rodents. In some places, pythons still use hay sheds and grain silos as an important place to find food. Unfortunately, like many native Australian species, pythons have declined in Victoria and parts of NSW due to the loss of habitat, the collapse of old hay sheds and declining food availability. In heavily modified farming landscapes, rabbits are the main prey of pythons and provide an extremely important high-energy food source. Carpet Pythons are also commonly kept as pets, and the new ‘designer’ morphs of various colour variants that are being produced by breeders around the world make them an extremely sought after species in the pet trade. Even in the wild, Carpet Pythons vary in colour and body pattern within and between different populations. Pythons on the south-east coast of Australia are often olive to black with a series of white or yellow diamond markings along the body, whereas pythons from the Murray–Darling catchment are dark grey with pale blotches, bands or stripes along the body. Photo by Damian Michael.

4 – R e p t il e s

113

micro-habitat in other vegetation types is extremely important because it is the main process by which sites are recolonised following local extinction events. In ecology, this concept is called meta-population theory, and helps explain the process of temporary local population extinction and colonisation. However, in practice, this process can only work effectively if the landscape the animals are trying to move through is not heavily cleared or disturbed.

Reptiles in woodlands surrounded by stands of pine In Chapters 2 and 3, we described the multi-faceted responses of birds and mammals inhabiting woodland patches where the surrounding landscape was being transformed from grazing paddocks to maturing stands of Radiata Pine. But how are reptiles faring in this same environment characterised by a mosaic of woodland patches and plantations? After 17 years of intensive reptile surveys, we were able to examine the response of two common species – the Southern Rainbow Skink and the Eastern Three-toed Earless Skink. We used data collected from our artificial refuges for use in the analysis and asked the question: •

What is the probability that these two species will colonise woodland remnants that are surrounded by grazing lands compared with woodland remnants surrounded by pines?

Why do so many snakes have dark markings on their heads? Most people are familiar with the large venomous snake species that occur in Australia – tigers, blacks, browns and taipans. Few people would be aware of the myriad of smaller species that also live alongside us – such as Dwyer’s Snake, Little Whip Snake, Red-naped Snake and Curl Snakes. These snakes have an average length less than 50 cm. All are venomous, but generally pose little danger to humans or livestock. These four species have a dark coloured head, which makes them superficially similar to juvenile of the Eastern Brown Snake. For small, mildly venomous snakes, resembling a more venomous species has its advantages, because predators may learn to avoid all snakes with dark coloured heads. Having a dark head also has other advantages. Many small species are active during the cooler months and during periods when ambient temperatures are relatively low. Rather than basking in the open, small species tend to be very cryptic and use their dark heads as a solar panel to heat up their entire body without fully emerging from cover. This way, small snakes are able to thermoregulate without the risk of being eaten by avian predators such as butcherbirds, Laughing Kookaburra and several species of raptors.

114

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Are Goannas really venomous? There are 74 species of monitor lizards, or goannas as they are commonly called, in the world. Australia supports 29 of these species. This group of lizards contain some of the world’s largest reptiles, including the Komodo Dragon and the Water Monitor from Indonesia, and the Australian Perentie and Lace Monitor. A common folk tale we commonly hear is that if you get bitten by a goanna, the wound will reappear every few years. For many years, people believed that the painful swelling and prolonged bleeding from their bites was due to infection and septicaemia as a result of their saliva being loaded with bacteria. And to some degree this is true, because most goannas feed on carrion. However, in 2005, researchers from the University of Melbourne discovered rudimentary venom glands in both goannas and the closely related iguanas. The venom gland runs down the side of the lower jaw and several toxins very similar to snake venom have been identified so far. This is even more reason to give goannas a wide berth at picnic grounds.

Our results showed that different species respond to changes in the landscape in different ways. For the Southern Rainbow Skink, the probability that this species would be detected in the woodlands surrounded by pines was significantly lower than in the woodlands surrounded by grazing land. By contrast, the probability that the Eastern Three-toed Earless Skink would be detected in the woodlands surrounded by pines was significantly higher than in the woodlands surrounded by grazing land. These two contrasting responses were linked to differences in thermal behaviour and mode of reproduction. The Southern Rainbow Skink is active by day and requires direct access to the sun to raise its body temperature above that of its surroundings. The dense shady pines create a barrier to dispersal and the risk of

Small snakes on the increase Species such as Dwyer’s Snake, Little Whip Snake, Red-naped Snake, Curl Snake and the Bandy Bandy play an important role in the environment because they are prey for many nocturnal predators, including large tree frogs, the Barking Owl and the Bush Stone-curlew. However, many of these small woodland snakes are rare and some are even threatened with extinction. Over the past few years, we have found numbers of small snakes are increasing in areas where livestock grazing has been excluded or reduced. One reason these species are increasing is that they are extremely sensitive to trampling, and high levels of soil disturbance and vibrations by hard-hoofed animals cause these animals to flee. When stock is removed from an area, these species tend to prosper and have a chance to rebuild population numbers.

4 – R e p t il e s

115

Curl Snakes living underwater Many species of snakes are aquatic or semi-aquatic. Classic examples are sea snakes (which feed and reproduce entirely in the sea) and sea kraits (which feed in the water but lay eggs and shelter on land). Many snakes also live in freshwater environments, with the South American Anaconda (which grows to over 8 m in length) being a classic example. We also have many aquatic or semi-aquatic species in Australia, including Macleay’s Water Snake, White-bellied Mangrove Snake, file snakes and the Water Python. Aquatic snakes are reptiles and need to breathe air. However, many species are able to remain underwater for extended periods without surfacing for air. They do this via a process called cutaneous respiration, whereby oxygen gas is exchanged through the skin. In some sea snakes, 30% of their oxygen uptake is achieved in this manner. This is quite a remarkable feature of aquatic snakes, but do terrestrial snakes that live on the land also have this ability? This area of research has been poorly studied, but in 2010, following a major flooding event in the NSW Riverina, we encountered several Curl Snakes sheltering beneath our artificial refuges (railway sleepers and corrugated iron), which at the time happened to be completely underwater. Curl Snakes are small venomous nocturnal species that grow to an average size of 40 cm. On returning to the same site 2 months later, we were surprised to see that floodwaters had not receded and the same artificial refuges (and snakes) were still submerged.61 This observation has led us to believe that Curl Snakes may have the ability to move at extremely cold temperatures and surface for air, but they also may have the ability to take up oxygen via cutaneous respiration. To test these assumptions we would need to establish experimental trials in the laboratory.

extinction for this species increases when pine plantations are created in woodland landscapes. By contrast, the Eastern Three-toed Earless Skink gains heat directly from warm substrates such as the ground. It is also nocturnal and has a much lower preferred body temperature than day-active species. This means that it has a greater ability of being able to survive in cool shady environments such as a pine plantation thereby increasing its chance of colonising woodland remnants. A further explanation is that the Rainbow Skink lays eggs that are unlikely to hatch in the cooler stands of pines tree, whereas the Three-toed Earless Skink gives birth to live young, which may temporarily survive in the pines.62

Concluding comments It is highly likely that the reptile fauna of agricultural landscapes has been significantly depleted over the past 200 years, although there is currently only limited empirical evidence for such changes. There are many key strategies that

116

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

farmers and other land managers can employ to promote the conservation of reptiles on farms. These strategies will have only limited impacts on the economic viability of farm enterprises. Two of the most important actions to improve reptile diversity are to protect rocky environments such as granite outcrops and areas of bush rock, and manage fallen timber in the landscape. Our findings also indicate that changing grazing regimes is likely to have important benefits for increasing reptile populations, thereby ensuring ample food resources for a wide variety of small native mammals and bird predators.

5 Invertebrates

Only 1% of the total number of animal species in most environments are vertebrates such as reptiles, mammals and birds. The other 99% are invertebrates, with much of that biodiversity being insects and other arthropods (e.g. spiders, centipedes and crustaceans). These animals not only comprise most of species on Earth, they also play many critical ecological roles, so much so that ecosystems would simply (and catastrophically) cease to function without them. For example, invertebrates are essential for effective pollination of crops, the dispersal of seeds, the breakdown of wastes and recycling of nutrients, and of course being an important food source for many birds, reptiles and mammals. Native invertebrates are also known to have an important controlling function of crop and pasture pest insects. Despite these fundamentally important ecological roles, remarkably little is known about the world’s invertebrates. We are not even sure of how many species there are, in part because the overwhelming majority are not formally described by scientists. We certainly know very little about what factors influence the distribution and abundance of invertebrate species (except for some very high profile pests such as the Plague Locust). In an attempt to take a small step in rectifying the massive knowledge gaps on invertebrates, we have completed studies on beetles, ants and butterflies in the agricultural landscapes of south-eastern Australia. A handful of research investigations have been completed and many more either await further exploration or commencement. The limited work instigated so far means that this chapter is shorter and far less detailed than the others in this book. We apologise

118

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

How are invertebrates studied in agricultural landscapes? Many different methods can be used to study invertebrates. The one used in most of our studies to date was to install micro-pitfall traps on the ground. These pitfall traps are 285 mL plastic cups that are dug into the ground so they are flush with the soil surface, and contain a solution that acts as a preservative. Pitfall traps typically capture ground-dwelling invertebrates, such as ants, beetles and spiders, but not those that live in other habitats such as the tree canopy or on the bark. Other approaches such as fumigating sections of the tree canopy are needed to survey invertebrates that are characteristic of other habitats. For our studies, pitfall traps were set along 200 m long transects that were located within long-term sites that had previously been established to survey for other animals such as possums, gliders and birds. The kinds of sites being surveyed varies between the different studies of invertebrates. Unlike work on vertebrates such as birds and mammals where almost all of the species are well known, investigations of invertebrates are made all the more difficult because most of species are difficult to classify to species level, or have not even been formally described by scientists! In addition, field surveys can quickly generate thousands of samples (often including many undescribed species). The solution to these pervasive problems that occur in almost all Australian terrestrial habitats (and indeed habitats in most parts of the world), is to sort especially diverse groups such as beetles into what are called ‘morphospecies’– that is, animals that superficially appear to be broadly similar organisms in terms of shape, size and colour. Morphospecies are generally considered to be reliable substitutes for species in the majority of families of beetles. In addition to sorting invertebrates into morphospecies, it is also possible to assign these animals to broad groups based on what they eat: herbivores, predators, fungivores and detritivores (which eat dead plant and animal matter). Other measurements of captured invertebrates also can be made, including body length and the presence of hind-wings, which reflects the mobility of animals. Understanding the diet and other life history features of beetles makes it possible to determine if there are broader relationships such as for example, that large, flightless beetles are more likely to inhabit long-undisturbed areas such as old growth forest.

for this lack of content, but our forays into the exciting and fascinating topics of invertebrate ecology have only just begun. This is, in part, because of the challenges in studying invertebrates (see Box above) and also because it is hard to get talented postgraduate students to work on these very species-rich but poorly known animals. We hope that if we were to rewrite this book in another 5–10 years, we would by then have completed many additional studies of the invertebrates inhabiting agricultural landscapes and that information would feature prominently in a new volume.

5 – Inver tebrates

119

The exotic honeybee is one of the most widespread invertebrates in woodland landscapes. The species obviously has important ecosystem roles, including in honey production but also in pollinating crops such as canola, as well as many native plants. Photo by Clement Tang.

Blue-banded bees belong to a genus of large, hairy and robust bees in the genus Amegilla. The species in this group typically nest in tunnels in the soil (although sometimes in the mortar between bricks). They nest in aggregations, although individual females make their own nest and construct wax-lined cells containing larvae. The larvae are fed ‘bee bread’ – dried pollen and honey. The nests of some species of Amegillid bees are sometimes parasitised by other species in this genus. Photo by Clement Tang.

120

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The honeybee is by far the most common species of invertebrate detected using nest boxes that we have established in plantings and woodland remnants. Bees are more likely to use nest boxes in woodland remnants than plantings, possibly because they gather more pollen and nectar from the large trees that characterise woodland remnants. Bees are more likely to occupy nest boxes in woodland remnants close to other woodland remnants. Photo by Tabitha Boyer.

Kangaroos and beetles Eastern Grey Kangaroos can reach high population numbers in grassy woodlands such as those around Canberra. This is largely due to the abundance of artificial water sources, both in nature reserves and adjacent farmland, and the absence of large predators such as the Dingo. High numbers of kangaroos can have substantial negative impacts on ground-layer plants in grassy woodlands, particularly during extended drought conditions. In particular, kangaroos eat many grasses and small native plants such as forbs (the name given to all broad-leafed herbaceous plants that are not related to grass). This creates what are called ‘grazing lawns’ – grassy areas that are kept very short. This not only prevents the plants from flowering and setting seed, but also retards the development of tussocks and a structurally complex ground-layer upon which many animals depend, including many insects. Research on this problem has been conducted in the Mulligans Flat–Goorooyarroo Woodland Experiment.65 Ground-dwelling beetles were sampled from inside and outside two large kangaroo exclusion areas. Within each of these areas, woody debris also was added in different configurations, ranging from 40 tonnes per

5 – Inver tebrates

121

hectare down to control sites with no woody debris. Two key findings became apparent after 2 years: (1) areas with reduced kangaroo numbers had a higher number of beetles including the weevil Cubicorhynchus sp. (see photo on p. 126); and (2) areas with woody debris added maintained beetle diversity even in the presence of high kangaroo numbers.54 Not only does this research demonstrate a negative effect on insects of high kangaroo numbers (approx. 2 animals per hectare or higher), but also that having a complex ground layer with lots of woody debris can help mitigate this effect by providing small structural ‘refuges’ for beetles, and likely many other insects and their predators such as skinks and small mammals.

Ants in grazing landscapes Research is currently underway on the ants occurring in the grazing landscapes around Cowra in NSW. This is part of the much larger Environmental Stewardship Program study. Approximately 100 sites have been selected on many farms with a range of different grazing strategies, including continuous and rotational grazing. On each farm, sites also have been established to exclude grazing to act as a control in the study. Many different kinds of data are being collected, including soil chemistry, ground-layer native and exotic plant cover, woody debris and litter cover. In addition, ants have been surveyed at most of these sites, yielding over 25 000 specimens from 92 different species, and resulting in one of the most comprehensive surveys of ants in this region. Ants are one of the most important insect groups in agricultural landscapes because they are closely linked to soil

Ants as indicators Ants have been used as biological indicators of environmental conditions for many years. This has included looking at ants to assess the rehabilitation progress of mining land, and the effects of livestock grazing on insect biodiversity. The presence or absence of different kinds of species of ants, and the total number of species, can be indicative of the condition or biodiversity of a grassland or woodland site. Australia has been at the forefront of research on ants as bioindicators, and pioneered the use of what are called ant ‘functional groups’ – groupings of species that behave in similar ways. For example, some ants feed on the seeds of different grasses, and perform an important role in the dispersal of these plants. Other ants eat the sugars produced by scale insects in eucalypts and wattles. Another example is ants in the Subfamily Dolichoderinae, which includes the Meat Ant (see photo on page 122). These ants are very good at discovering and dominating new food sources, and can exclude other ants or insects from some sites. These kinds of broad groupings of ants has been very useful for indicating how different kinds of disturbance, impact on certain kinds of species and affect overall biodiversity in agricultural landscapes.66–68

122

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Meat Ant is an abundant animal that prefers woodland sites with native groundcover. This species typically dominates food resources where it occurs. Photo by Philip Barton.

The Green-head Ant is an opportunist species found in more disturbed sites, such as areas with higher levels of grazing or exotic grass cover. Photo by Philip Barton.

5 – Inver tebrates

123

Ground-dwelling invertebrates such as ants, beetles and spiders are collected using pitfall traps. (Left) Researcher Philip Barton digging in a pitfall trap next to a log. (Right) A close-up of a pitfall trap that has been dug in flush with the ground surface. A small amount of non-toxic preservative is placed at base of the trap to capture specimens. Photos by Philip Barton.

health through their nesting and burrowing activities. This results in greater water infiltration and the movement of nutrients underground through the movement and hoarding of seeds and dead insects. So far, results suggest that broadly grouping farms by grazing history does not explain the diversity and composition of ant assemblages very well. Instead, it is the detailed habitat characteristics at each individual site that seem to be more important for determining which ants are found. For example, less grass biomass and more tree stems were associated with the competitively dominant Meat Ant, whereas higher cover of exotic grasses was associated with the opportunist Green-head Ant (see photo on p. 122). Ongoing research will look more closely at the links between grazing history, site attributes and associated ant fauna. This will reveal new information about how different grazing strategies can affect the occurrence of ant species and their role in soil health.

Butterflies in grazing landscapes A major study has been comparing use by butterflies of farmland areas and Radiata Pine plantation-dominated landscapes.69 The work is taking place in the

124

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

A study by the ANU team has focused on how butterflies respond to extensive areas of Radiata Pine plantation that surrounds remnant patches of temperate woodland. The study examined two native species (the Common Brown Butterfly and the Common Grass Blue Butterfly), as well as one introduced pest species (the Cabbage White Butterfly) that has been in Australia since 1929. Both the Common Grass Blue Butterfly and the Common Brown Butterfly are common and widespread species, although they tend to avoid stands of Radiata Pine. Photos of Cabbage White and Common Grass Blue by Clement Tang, Common Brown by Chris MacGregor.

5 – Inver tebrates

125

Bees and nest boxes Feral honeybees are one of the most common inhabitants of nest boxes in agricultural landscapes. Between 3 and 7% of the 334 nest boxes established in our studies in southern NSW were occupied by honeybees; almost three times the rate of occupancy of the next two most commonly recorded species (the Yellow-footed Antechinus and the Common Brushtail Possum). Problems with nest box use by honeybees are generally most widespread and common in areas subject to extensive human disturbance and this appears to extend to areas of woodland close to roads such as those adjacent to the Hume Highway that were targeted in this study. In addition, nest boxes close to water are often occupied by bees – although boxes with hives will sometimes subsequently be used by possums and the Yellowfooted Antechinus. Feral honeybees are known to compete for hollows with other cavity-dependent species, including some mammals. However, it remains unclear whether competition has overall impacts on populations of a given mammal species or if a given individual animal simply finds and occupies an alternative hollow that has not been colonised by bees. The effects of competition between honeybees and native hollow-using animals need to be better understood. This is especially important if well-intentioned nest box programs actually result in increased numbers of honeybees, leading to negative effects on the native animals the nest boxes were installed to assist.

Nanangroe region between Gundagai and Tumut where former grazing paddocks have been converted to intensively managed Radiata Pine stands. The research entailed repeated surveys of butterfly species, as well as release experiments where

Beetles perform many important ecological roles in woodland ecosystems. The ANU team is surveying beetles to understand how landscape changes have affected their diversity. This work has shown there are three functionally distinct beetles that occur in grassy woodlands and grazing landscapes. (Left) A small predatory beetle (Family Carabidae) will eat many other kinds of smaller invertebrates. (Centre) Dung beetles (Family Scarabaeidae) are a common sight in grazing landscapes and help to break down the dung of livestock and kangaroos. (Right) A species of weevil (Family Curculionidae) with a characteristic long ‘rostrum’ that allows it to bore into plant stems and seeds. Photos by Philip Barton.

126

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Over-abundant populations of kangaroos can have significant negative impacts on woodland condition and woodland biodiversity. (Left) A kangaroo grazing exclusion fence shows the grass with seed heads on the left and a heavily overgrazed area on the right. (Right) The weevil Cubicorhynchus sp. is one of many species found to be significantly more abundant in areas with lower kangaroo densities. Photos by Philip Barton.

animals were caught and then released adjacent to different kinds of (woodland and pine) habitats and their behaviour observed. The surveys revealed that woodland patches on farmland provide suitable habitat for two native species of butterfly – the Common Brown Butterfly and the Common Grass Blue Butterfly, as well as the introduced Cabbage White Butterfly. By contrast, no butterflies occurred in pine plantations. Amazingly, woodland patches surrounded

The effects of livestock grazing on invertebrates is not well understood. Extensive pitfall trapping of ants and beetles in a range of locations is endeavouring to improve knowledge of which kinds of species respond positively and negatively to different kinds of grazing regimes. This photo shows one of hundreds of sites that have been targeted for surveys of invertebrates. Photo by Daniel Florance.

5 – Inver tebrates

127

Although the European Honeybee is common and widespread, there are also many species of native bees that occur in temperate woodland environments. We have deployed blue vane traps to capture more than 20 species of bees. Photo by Daniel Florance.

by pine plantations supported a greater abundance of butterflies than similar kinds of woodland patches on farmland.69 It appears that pine plantations are not only totally unsuitable habitat for butterflies, but such exotic environments are also barriers to movement. This means that the density of populations inhabiting woodland patches surrounded by pine stands is elevated by individuals being reluctant to disperse beyond the place where they hatched – an ecological phenomenon called a ‘fence effect’. That is, animals are ‘fenced into’ suitable patches by highly unsuitable environments that are hostile for dispersal.69 Two factors seem to be key drivers of the unsuitability of pine plantations for butterflies – the paucity of host plants that provide food and egg-laying sites and the limited amount of light in densely stocked stands of trees. Notably, capture and release experiments showed that butterflies almost never crossed pine plantations from adjacent paddocks or woodland patches. Even in the rare cases that butterflies crossed in areas of pine plantation, they very quickly returned to paddocks or woodland patches, suggesting they actively avoided exotic conifers.69

Many species of bees are a challenge to identify. The best approach to determining which species are present is to create a reference collection of pinned animals. Any new individuals that are caught can be matched against the set of species in the reference collection. Our reference collection includes a wide range of different kinds of bees including blue-banded bees, reed bees (which are among the smallest and least known of the social bees), sweat bees, and leafcutter bees (which can often be identified by their large jaws that they use for cutting pieces of leaves in nest construction). Photo by Ding Li.

128 W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

5 – Inver tebrates

129

Spiders are an important part of woodland ecosystems and play many important ecological roles. They are food for animals such as the Yellow-footed Antechinus and the Southern Marbled Gecko and their webs are used as nesting material by birds such as the Willie Wagtail. Some kinds of spiders create burrows that are then used by other animals such as small reptiles. There are a very large number of species of spiders in woodland environments and three spectacular ones include the Mouse Spider, the Web-casting Spider and the Banded Huntsman. Photos by Mason Crane and Damian Michael.

In summary, the work to date has indicated that landscape transformation resulting from pine plantation establishment can have substantial impacts on butterflies, with these insects actively avoiding stands of exotic conifers and not moving through these areas.

‘Bugs’ and pines – what happens to invertebrates in eucalypt patches surrounded by pine plantations A key question, given the large number of critical ecological roles played by invertebrates; is: •

How do invertebrates respond to landscapes being converted to plantations?

A major study of ants, flies and beetles in eucalypt woodland and forest patches surrounded by pine stands was completed by Smith in 2006.70 The work involved

130

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

surveys of animals in pine stands and in small, medium and large patches of native vegetation. Different groups of invertebrates exhibited quite different responses. Ants and flies were uncommon in stands of Radiata Pine and species richness and overall abundance was highest in sites located in largest eucalypt patches. In contrast, beetle species richness in stands of Radiata Pine was similar to that in large eucalypt patches. Overall beetle abundance was highest in the large eucalypt patches. Although stands of Radiata Pine were inferior environments for all groups, beetles and flies were relatively common and species-rich within them. This contrasts strongly with the results for butterflies (see above) – a group of invertebrates almost entirely absent from plantation-dominated areas.69

Concluding comments Invertebrates are an extremely important component of all ecosystems, including those dedicated (or partially dedicated) to agricultural production. Many factors influence the occurrence of these often very poorly studied animals such as ants, beetles, butterflies and bees. These factors include grazing by domestic livestock, overgrazing by kangaroos and establishment of plantations. Other factors likely to have an important effect on invertebrates, but that we have not examined to date, include woodland patch size and shape, as well as the condition of the vegetation within those patches.

6 Vegetation cover and plants

Introduction Many of our studies examine relationships between vegetation cover and animal occurrence. That is, the role of vegetation as habitat for animals. Of course, vegetation is much more than just habitat for animals – it is a critically important component of biodiversity on farms in its own right. Some environments such as rocky outcrops can be hotspots for plant diversity, including many plant species that are rarely found elsewhere in agricultural environments.61 Therefore, although trees dominate the native vegetation cover in agricultural areas, there is much more to vegetation cover than patches of trees. In this chapter, we discuss some of our findings about the vegetation in agricultural landscapes, ranging from how the amount of cover is changing over time through to which characteristics of remnants and replantings are important to make them effective habitats for biodiversity.

Increase in vegetation cover over time The temperate eucalypt woodlands of eastern Australia are some of the most extensively modified ecosystems in Australia, if not the world.9,71 This has occurred as a result of several phases of intensive land clearing to establish grazing

132

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

How vegetation is studied in woodlands – field survey protocols There are many ways to study vegetation in agricultural environments and we have used several approaches. The first is to complete detailed assessments of plots of a fixed size (typically 20 m × 20 m) and carefully record the number of individual plants of each species. In addition, the structure of the vegetation is measured, including the prevalence of large old hollow-bearing trees, the abundance of large logs, the number of different vegetation layers (ground, shrub, understorey and overstorey), the amount of cover of each layer, and the overall total number of living and dead stems. Usually several plots are measured at any given site to avoid the risk that any given single plot is a poor representative of the vegetation on that site. Therefore, we typically have between 3 and 5 plots along the permanent 200 m transect that we establish at each of the 847 sites in our long-term, large-scale studies in agricultural environments. These surveys are repeated on a regular basis, enabling us to quantify changes in vegetation cover and condition over time. A second part of our vegetation surveys is to conduct site-wide assessments of the vegetation by measuring attributes that characterise entire patches, such as patch size, patch shape and the position of the patch in the landscape (e.g. in a gully or on a ridge). Third, we measured the landscape context of sites by assembling information on the amount of native vegetation in the landscape surrounding a site, and the condition of paddocks in which a site is located, and other similar kinds of attributes. Another way we gather vegetation information is to use data derived from satellites. This provides information on the total amount of woody native vegetation cover at particular scales (e.g. at a site, on a farm or across a landscape). Examining a sequence of satellite images taken at several points in time (e.g. annually between 2000 and 2014) enabled us to determine if the amount of cover is increasing, decreasing, or remaining the same. It also provides information on which farms and in which landscapes vegetation cover has changed.

pastures and croplands. The impacts of widespread clearing on such environmental problems as soil degradation, soil acidification, secondary salinity, and biodiversity loss are well documented.72,73 Concerted actions to tackle these problems by many farmers and natural resource management groups (such as Catchment Management Authorities, Local Land Services, Landcare and Greening Australia) have been underway for several decades, but have things changed in that time? We therefore posed the question: • Is there a demonstrable improvement in vegetation cover over time? Our work over the past two decades has revealed significant changes in agricultural landscapes. For example, the amount of woody vegetation cover in the South West Slopes region – one of the most cleared and modified regions in NSW – has increased by 3.5% in the last decade. Importantly, this is a result mirrored by

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

133

Rocky outcrops are important because they provide refuges for fire-sensitive plants. This is one of the characteristic features of the vegetation that grows on rocky outcrops – they support a high proportion of plants that reproduce from seed and germinate when light and moisture conditions are favourable, as opposed to fire-adapted species that regenerate primarily from epicormic buds or underground rhizomes. Examples of ‘obligate seeders’ include genera such as Callitris, Acacia, Pultenaea and Dodonaea, whereas ‘resprouters’ include various eucalypt species. Fires are occurring more frequently in rocky areas due to an increase in accidental and ecological control burns. Increased fire frequency can have long-lasting effects on the vegetation of rocky outcrops because the number of fire-sensitive species is reduced and fire-adapted species become more widespread, resulting in more flammable vegetation and higher intensity fires in the future. The species in this collage include clockwise from top left: a rocky outcrop with Hairy Wattle understorey, Flat-leaf Bush-pea, Dwyer’s Red Gum, Common Fringe-myrtle, Nodding Blue-lily, Rock Isotome, Woolly Ragwort and Blanket Fern. Photos by Damian Michael.

the work of colleagues working in other regions such as Central Victoria.74 It seems likely that these positive increases in vegetation cover are the result of at least two factors. First, they reflect the enormous efforts in replanting programs aimed at

134

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

There are more than 20 species of mistletoes in eastern Australia and these plants provide food, nesting and sheltering for many bird species, as well as numerous insects (which are preyed on by birds). It is not surprisingly then that more mistletoe leads to more birds. Several studies have shown that plantings and remnants with more mistletoe support more species of birds. These include a suite of bird species of conservation concern including the Restless Flycatcher, White-browed Babbler, Brown Treecreeper, Crested Shrike-tit, Black-chinned Honeyeater and Dusky Woodswallow. Some species such as the Mistletoebird (see photo on p. 53) and the Painted Honeyeater are intimately associated with mistletoe. Photos by Dave Blair and Mason Crane.

restoring native vegetation cover. Second, much of the past decade has encompassed the period of the Millennium Drought during which livestock numbers were reduced. This has, in turn, enabled natural regeneration to occur. The combination of replanting and natural regeneration has therefore underpinned the major and positive increases in vegetation cover documented for the South West Slopes region. Importantly, at the same time there have been significant increases in the amount of native vegetation cover, there also have been changes in the occurrence of native birds (Chapter 2) and some species of native mammals (particularly arboreal marsupials; see Chapter 3). Moreover, there are strong links between the change in vegetation and the change in animals.1,35 This underscores the environmental benefits that can accrue from efforts to improve the cover of vegetation in agricultural landscapes.

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

135

Does changing the cover of native woody vegetation have impacts on the local and regional climate? A question we have often been asked by farmers is: ‘Is there a positive effect of vegetation cover on climatic conditions such as rainfall and temperature?’ This is an interesting question because in the past, some farmers have suggested that rain ‘follows the trees’ whereas other landholders have believed that ‘rain follows the plough’. Both were proposed before the development of ecology as a rigorous scientific discipline. Recent work, including several studies in Australia, has suggested that rainfall patterns and vegetation cover are linked at the regional level. First, McAlpine and colleagues analysed large climate and vegetation cover datasets and their results suggested that the effects of the Millennium Drought were magnified in those areas where clearing was most pronounced.75 Second, studies of rainfall gradients in south-western Australia indicate a decline in precipitation from the coast to inland areas over the largely cleared wheatbelt. However, the rainfall increases again beyond the inland edge of the wheatbelt and where native vegetation cover is relatively intact. Similar kinds of patterns in rainfall have been seen at very large scales such as across the Amazon Basin in South America. What is happening in these (and many other) well-documented cases? Part of the answer lies with the ecological roles trees play in transpiring moisture through their leaves to the atmosphere. This linking role means that there is more moisture in the atmosphere above treed environments than over cleared landscapes. When passing weather cells move through an area, that moisture is then returned to the land surface as precipitation.76 There are, however, additional links between climate change and rainfall effectiveness. For example, as climates warm, more rain is needed because evaporation outstrips precipitation. Therefore, there may well be quite marked changes in hydrology with climate change, with effects well beyond simply how much rainfall occurs.77

Changes in vegetation attributes over time Everyone with a garden or farm knows that trees, shrubs, and grasses change over time. What is rarely done, however, is to carefully record and document how much stands of trees and shrubs and swards of grasses and other groundcover plants, germinate, grow, mature and die over prolonged periods of time. We have sought to do this as part of our long-term research on patches of remnant woodland and within plantings. This is achieved through repeated surveys of the vegetation at all of our long-term monitoring sites. For example, in the case of plantings, we have found that some attributes have remained largely unchanged over the past 15–20 years, such as the amount of bare earth and the amount of understorey cover. However, other characteristics of plantings have exhibited marked changes during

136

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

In many cases, paddock trees are all that remains of the past landscape on a farm – the residual elements of the woodland vegetation that used to cover an area. Many people remain unaware of the extent of past vegetation clearing: tens of billions of trees have been removed from agricultural landscapes in the Murray– Darling Basin alone. As outlined in several places in this book, paddock trees play many important ecological roles. One of the most critical is that they provide the source of seed for the natural regeneration of new cohorts of young trees that can eventually help replace older trees when they senesce and eventually die. Indeed, this is often a more cost-effective way of restoring the vegetation cover of an area than replanting. Photo by Damian Michael.

The structure of remnant woodlands and plantings has a significant impact on the suitability of these environments as habitat for many plants and animals. Logs are a key component of woodland vegetation structure. Animals such as the Brown Treecreeper and the Yellow-footed Antechinus are strongly associated with logs. But these are just two of a myriad of native species that the team from the ANU have found to be more likely to occur where logs are present. These range from the tiny Yellow-rumped Thornbill through to the Common Ringtail Possum. Logs also help protect the ground layer of woodlands (and associated populations of native invertebrates) from over-browsing by high populations of the Eastern Grey Kangaroo. The areas immediately adjacent to large logs are also places where leaf litter accumulates and natural regeneration of native plants is more likely to occur. Large logs also have a more direct practical role on farms such as providing shelter from inclement weather for young lambs. Photo by Damian Michael.

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

137

Plantings are an increasing common sight on farms in southern NSW and north-eastern Victoria. An increasing body of work is showing how important these places are for birds, although not all species respond positively to these restored environments. Mammals and reptiles appear to take longer to colonise plantings than some species of birds and long-term monitoring is needed to determine how effective these areas will be over time. Plantings also have positive benefits for other kinds of vegetation on a farm. For example, the condition of paddock trees is better maintained, or sometimes even significantly improved, when they are surrounded by replanted woodland. Similarly, plantings can help tackle problems with secondary salinity on a farm and this too can reduce the risk of deteriorating tree health for other areas of native vegetation on a farm, particularly large old scattered paddock trees. Photo by Chris MacGregor.

Woodlands sometimes cannot regenerate because of intensive grazing pressure by livestock (and other herbivores such as rabbits and kangaroos). This can result in vegetation cover being dominated by scattered paddock trees and very little else. As paddock trees age but fail to be replaced by new cohorts of trees, there is a risk that almost all native tree cover will be lost. There are several ways to encourage natural regeneration on a farm. One is to reduce grazing pressure around paddock trees, even only temporarily (for 2–3 years) to allow young trees to germinate and grow sufficiently tall that key growing points are not eaten by herbivores. Organisations such as Greening Australia have helped many farmers implement whole-ofpaddock regeneration programs that can help restore much needed vegetation cover. Another strategy is to fence off areas around paddock trees to control grazing pressure and thereby promote natural regeneration. Photo by Dave Blair.

138

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Temperate native grasslands are among Australia’s most cleared and heavily modified ecological communities nationwide. Less than 1% native grassland cover remains in many agricultural districts in southern Australia. The biodiversity value of these seemingly simple ecosystems is often very poorly understood. However, a range of different studies have highlighted the importance of temperate native grasslands, not only for native plant species, but for a wide range of birds of conservation concern as well as many species of skinks, legless lizards and mammals. Our long-term survey data has clearly shown that bird species richness is significantly higher on farms that support native grassland (in addition to other vegetation assets such as woodland remnants, plantings and scattered paddock trees). Woodland patches that have a ground cover dominated by native grassland also support more bird species than patches where the ground cover is absent or comprised primarily of exotic grasses. Photo by Damian Michael.

this period. These include the height of the canopy, the depth of the canopy trees (although this tends to plateaux from ~15 years after establishment) and the amount of cover of the overstorey trees. These changes in the structure of the vegetation in plantings may be one of the reasons why these areas support more species of birds over time (primarily in winter; see Chapter 2). They also may explain why there are large differences in the species of birds that occur in young plantings compared with older plantings. However, some components of the vegetation take far longer than 1–2 decades to be recruited to plantings: large logs and large old hollow trees are two key examples and both provide critical habitat for a wide range of both vertebrate and invertebrate native animals.

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

139

Rocky outcrops often support several rare and endemic plants. The Woolly Ragwort is a threatened species of daisy that is known from approximately a dozen isolated populations growing near the base of rock outcrops in southern NSW. This species is capable of regenerating from seed when conditions are right, but it can also sprout new shoots after fire. Senecio species are often the first plants to recolonise an area after fire and are a favourite food source for the caterpillar of the native Tiger Moth. The main threats to this species are weed invasion, clearing of understorey plants on private property and rural subdivision. Photo by Damian Michael.

140

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Bush-peas are a large group of flowering native plants that belong in the Family Fabaceae. They are often a dominant component of the understorey of woodlands and can form dense thickets along roadsides that are frequently burnt or disturbed by earth works. Bush-peas, especially species in the genus Pultenaea, play an important role in cycling nutrients because they fix nitrogen from the atmosphere, which is then stored in specialised root nodules. When the plant dies, the fixed nitrogen is released into the soil and becomes available to other plants. Species such as the Grey Bush-pea (pictured) and the Flat-leaf Bush-pea (or Granite Bush-pea) grow on poor shallow soils at the base of rocky outcrops and provide a valuable source of fertiliser to surrounding plants. Photos by Damian Michael and Arthur Chapman.

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

141

There are over 950 species of wattles in Australia. Many of them have the common name Hickory Wattle, presumably because the wood is strong and hard similar to the northern hemisphere species of true hickory. Most wattles are short lived but some species such as Acacia penninervis (pictured) and Acacia implexa can live for up to 30 years. These wattle species grow on a variety of soil types but are often found in shallow soils and on rocky outcrops. Land clearing and habitat fragmentation can reduce the ability of these species to exchange genes across the landscape, resulting in genetically isolated populations. Researchers have suggested that introducing new germplasm from genetically viable source populations may be required to ensure the long-term survival of wattle species that have isolated populations. Photo by Damian Michael.

The Bulbine Lily was once a very common forb through temperate woodlands. Like many other forbs, it is now found only as small, isolated and disjunct patches. The Bulbine Lily produces a plump corm under the fleshy onion-like leaves at its base. The tuber-like corm was cooked and eaten year-round by Aboriginal people. This species used to grow in small thickets that made it easy to harvest. Photo by Damian Michael.

142

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

Box Gum Grassy Woodland is a highly endangered vegetation community that has been extensively cleared. High-quality remnants of this community can be found in travelling stock reserves, along railway lines and in old cemeteries. One of the characteristic features of this type of woodland is that the understorey consists of native grasses, orchids and a diverse range of wildflowers. Many of these groundcover plants are pollinated by animals, especially insects, and the plants generally provide a food reward for this service. However, many orchids achieve pollination by deceiving their pollinators with false promises of food. They do this by advertising bright colours or by exuding floral scents that imitate female insect sex pheromones, which effectively attract pollinator species such as wasps. The relationship between pollinator and orchid is so intricate that in some cases a single wasp species is responsible for pollinating a specific orchid. The species in this collage include clockwise from top left: Black-tip Greenhood, Chocolate Lily, Common Fringe Lily, Broughton Pea, Purple Burr-daisy, Common Crowfoot, Early Nancy and Waxlip Orchid. Photos by Damian Michael.

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

143

During winter and spring months, the understorey of good quality woodland remnants can be a mass of flowering shrubs. Bush-peas, also known as egg and bacon plants, can form dense thickets, especially following fire. These species provide insects with nectar and support critical nesting habitat for many threatened woodland birds. Some native woodland plants are cultivated by the horticultural industry and have become popular garden plants. The Native Lilac or Purple Coral Pea is a flowering evergreen climber that produces masses of violet coloured pea-like flowers. Many different cultivated varieties of this species are now available in white or pink flowering forms. Photo by Damian Michael.

How management interventions changes and improves vegetation Management actions such as fencing and stock control are widely advocated as part of integrating agricultural production and conservation, but: •

Do these actions lead to demonstrated changes in the condition of vegetation and, in turn, improved habitat quality for animals such as birds and reptiles?

This is obviously a critical question, because if improved management does not produce the desired results, then truly colossal amounts of money invested in environmental programs is being wasted. We sought to determine if management interventions such as planting, stock control, weed control and fencing were leading to changes in vegetation condition. This involved comparing the vegetation condition of sites where traditional (‘business as usual’) production grazing was conducted with sites where an incentive scheme had been implemented and payments were made to farmers to fence remnants or limit stock access to improve the vegetation cover.15 Some of

144

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The Kurrajong is a native Australian tree that is closely related to the Flame Tree and Bottletree. Kurrajong trees are extremely useful plants and were often spared from land clearing because the leaves provide valuable fodder for livestock in times of drought. In heavily cleared landscapes, it is not uncommon to find that the only remaining overstorey species are large old Kurrajong trees, especially on and around rocky outcrops. Indigenous Australians also have many uses for this plant – the tubers and seeds can be roasted and eaten, the bark can be made into fishing lines and the wood fashioned into shields. This species has become a popular street tree and many different cultivated varieties now exist. It has even been exported to places such as South Africa, North America and parts of the Mediterranean. Photo by Damian Michael.

these incentive scheme sites had been subject to vegetation management for just a few years, whereas for others the incentive scheme had been in place for almost a decade. We then compared the attributes of the vegetation in these three broad kinds of sites with the vegetation found in travelling stock reserves, which are typically ‘benchmark areas’ where the vegetation had been less disturbed than almost everywhere else throughout agricultural landscapes. The studies of vegetation condition and cover involved completing detailed measurements of many attributes of the vegetation over several years at over 100 sites. The results of this work were striking. The amount of bare ground was significantly lower, the diversity of native plant species was much higher, and the amount of natural regeneration was much greater on sites subject to incentive scheme management than on sites where traditional set stocking grazing regimes were employed. Moreover, the condition of the vegetation was typically much better (and the number of exotic weed species was significantly lower) where the

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

145

Geology plays an important role in influencing the types of plants and ecological vegetation communities that grow in the landscape. Soil cover over certain bedrocks can be very thin or absent, and different soil types can vary in nutrient composition, water-holding capacity and susceptibility to erosion. For example, soils derived from serpentine rocks are poor in major plant nutrients such as silicon, phosphorous, potassium and calcium, and high in certain potentially toxic elements such as magnesium, iron and nickel. Plants that grow on these types of unfertile soils are slow growing, compact, have narrow leaves and are characteristically different from plants that grow on deep fertile soils. Basalt soils derived from volcanic activity can be relatively fertile and often support rich and diverse grassland communities. Soils derived from granite rocks support some of Australia’s tallest wet forests and in high rainfall regions these soil types are suitable for tree plantations and crop production. The application of fertiliser in agricultural areas to increase soil nutrients is controversial, because although the practice increases crop yields it also has the unfortunate side effect of reducing native plant diversity and increasing exotic plants. Photo by Damian Michael.

incentive schemes had been employed for longer than where it had only recently been established. This was a very positive outcome, although both the short- and long-term incentive scheme sites still required a lot of additional improvement before the vegetation of such areas began to resemble that of travelling stock reserves.43 As outlined in Chapter 2 on birds, the positive changes in vegetation cover and condition also contributed to significant positive changes in the composition of the bird assemblages, with such places typically supporting more small-bodied native birds, including a suite of species of conservation concern. An important outcome of this work is that it is now possible to clearly demonstrate that incentive schemes can work and we have shown that significant

146

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

improvements in vegetation cover can be affected by actions such as altering the intensity of grazing by livestock.

Where in landscapes are key vegetation structures most likely to occur? Not all parts of landscapes are created equal when it comes to supporting components of vegetation structure that can be important for plant biodiversity, as well as habitat for particular groups and species of animals. It is now very clear what vegetation attributes are important for biodiversity. An important subsequent question is: •

Where are these vegetation attributes most likely to occur and why they occur where they do?

A detailed study of the vegetation in the South West Slopes region of NSW has shown that a combination of land management history and environmental factors influences where in landscapes vegetation structures such as logs, large old trees and swards of native grass are most likely to occur or be most abundant.78 These analyses have produced some fascinating results: • •

• • •

The abundance of hollow-bearing trees was greatest in old growth woodland, fenced areas and woodlands with a north-facing aspect. The abundance of medium-sized trees was greatest in regrowth sites and especially those with a north-facing aspect. There also was a landscape effect, with more medium-sized trees on those sites where there was a high level of native vegetation cover in the surrounding landscape. The areas supporting the highest abundance of logs were those in old growth woodland that had been fenced. Areas supporting the greatest amounts of native grass cover were those in low-lying areas of farms where the surrounding landscape was characterised by a high level of native vegetation cover. The amount of leaf litter was greatest on those sites where there was a large amount of native vegetation cover in the surrounding landscape.

These results have some significant implications for management because they suggest where in farming landscapes particular management practices are likely to be most effective (see Fig. 6.1). For example, by fencing north-facing old growth remnants, land managers can conserve five times the number of hollow-bearing trees that would be maintained in regrowth remnants on south-facing slopes. Similarly, by fencing old growth sites, managers can maintain (on average) 60% more logs per hectare than on unfenced regrowth sites.78 The specific management recommendations resulting from this work are summarised in Chapter 7.

6 – Ve g e t a t i o n c o v e r a n d p l a n t s

147

Fig. 6.1.  Summary of key strategies to enhance important vegetation structures and features on farmland.

148

W il d li f e C o n s e r v a t i o n i n F a r m L a n d s c a p e s

The loss of large old hollow-bearing trees a key threatening process in agricultural landscapes Large old hollow-bearing trees are among the most critical elements of habitat for wildlife in agricultural landscapes. These kinds of trees have a disproportionately large value in Australia where more than 300 species of vertebrates are dependent on them for nesting, roosting and other key ecological functions.10 Despite the importance of these trees, populations of them are declining rapidly in many agricultural landscapes around the world, including Australia.9 This is occurring for many reasons including deliberate removal for firewood, prolonged high-intensity grazing (which prevents the recruitment of new cohorts of trees), dieback, and fire (which often kills or even totally consumes large old trees). For example, as a result of these processes, in south-eastern Australia, tens of millions of hectares of intensity grazed temperate eucalypt woodlands have been predicted to support