Bird Conservation: Global evidence for the effects of interventions (Vol. 2) (Synopses of Conservation Evidence, Vol. 2) [1 ed.] 1907807195, 9781907807190

Citation preview

Bird Conservation

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Bird Conservation Global evidence for the effects of interventions David R. Williams, Robert G. Pople, David A. Showler, Lynn V. Dicks, Matthew F. Child, Erasmus K. H. J. zu Ermgassen and William J. Sutherland

Synopses of Conservation Evidence, Volume 2

Pelagic Publishing | www.pelagicpublishing.com

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Published by Pelagic Publishing www.pelagicpublishing.com PO Box 725, Exeter EX1 9QU Bird Conservation Global evidence for the effects of interventions Synopses of Conservation Evidence, Volume 2

ISBN 978-1-907807-19-0 (Pbk) ISBN 978-1-907807-20-6 (Hbk) Copyright © 2013 William J. Sutherland

This book should be quoted as Williams, D. R., Pople, R. G., Showler, D. A., Dicks, L. V., Child, M. F., zu Ermgassen, E. K. H. J. and Sutherland, W. J. (2013) Bird Conservation: Global evidence for the effects of interventions. Exeter, Pelagic Publishing. All rights reserved. Apart from short excerpts for use in research or for reviews, no part of this document may be printed or reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, now known or hereafter invented or otherwise without prior permission from the publisher. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library.

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Contents Advisory board About the authors Acknowledgements 1. About this book

xiv xv xvi 1

2. Habitat protection Key messages 2.1. Legally protect habitats 2.2. Ensure connectivity between habitat patches 2.3. Provide or retain un-harvested buffer strips

7 7 8 9 10

3. Education and awareness raising Key messages 3.1. Raise awareness amongst the general public through campaigns and public information 3.2. Provide bird feeding materials to families with young children 3.3. Enhance bird taxonomy skills through higher education and training 3.4. Provide training to conservationists and land managers on bird ecology and conservation

13 13 13 14 14 14

4. Threat: Residential and commercial development Key messages 4.1. Angle windows to reduce collisions 4.2. Mark or tint windows to reduce collision mortality

15 15 15 15

5. Threat: Agriculture Key messages – All farming systems Key messages – Arable farming Key messages – Livestock farming Key messages – Perennial, non-timber crops Key messages – Aquaculture

17 17 20 21 23 24

All farming systems 5.1. Support or maintain low-intensity agricultural systems 5.2. Practise integrated farm management 5.3. Food labelling schemes relating to biodiversity-friendly farming 5.4. Increase the proportion of natural/semi-natural vegetation in the farmed landscape 5.5. Pay farmers to cover the costs of conservation measures 5.6. Cross compliance standards for all subsidy payments 5.7. Reduce field size (or maintain small fields) 5.8. Provide or retain set-aside areas in farmland 5.9. Manage hedges to benefit wildlife 5.10. Plant new hedges 5.11. Manage stone-faced hedge banks to benefit birds 5.12. Manage ditches to benefit wildlife 5.13. Protect in-field trees 5.14. Plant in-field trees

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25 25 25 25 25 27 36 37 37 42 44 44 45 46 46

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Contents 5.15. Tree pollarding and tree surgery 5.16. Plant wild bird seed or cover mixture 5.17. Plant nectar flower mixture/wildflower strips 5.18. Create uncultivated margins around intensive arable or pasture fields 5.19. Plant grass buffer strips/margins around arable or pasture fields 5.20. Use mowing techniques to reduce chick mortality 5.21. Provide refuges in fields during harvest or mowing 5.22. Mark bird nests during harvest or mowing 5.23. Relocate nests at harvest time to reduce nestling mortality 5.24. Make direct payments per clutch for farmland birds 5.25. Control scrub on farmland 5.26. Take field corners out of management 5.27. Reduce conflict by deterring birds from taking crops Arable farming 5.28. Increase crop diversity 5.29. Implement ‘mosaic management’ 5.30. Leave overwinter stubbles 5.31. Plant nettle strips 5.32. Leave unharvested cereal headlands within arable fields 5.33. Plant crops in spring rather than autumn 5.34. Undersow spring cereals, with clover for example 5.35. Plant more than one crop per field (intercropping) 5.36. Revert arable land to permanent grassland 5.37. Reduce tillage 5.38. Add 1% barley into wheat crop for corn buntings 5.39. Leave uncropped, cultivated margins or plots (includes lapwing and stone curlew plots) 5.40. Create skylark plots 5.41. Create corn bunting plots 5.42. Plant cereals in wide-spaced rows 5.43. Create beetle banks Livestock farming 5.44. Maintain species-rich, semi-natural grassland 5.45. Reduce management intensity on permanent grasslands 5.46. Reduce grazing intensity 5.47. Provide short grass for waders 5.48. Raise mowing height on grasslands 5.49. Delay mowing date or first grazing date on grasslands 5.50. Leave uncut rye grass in silage fields 5.51. Plant cereals for wholecrop silage 5.52. Maintain lowland heathland 5.53. Maintain rush pastures 5.54. Maintain traditional water meadows 5.55. Maintain upland heath/moor 5.56. Plant Brassica fodder crops 5.57. Use mixed stocking 5.58. Use traditional breeds of livestock 5.59. Maintain wood pasture and parkland 5.60. Exclude grazers from semi-natural habitats (including woodland) 5.61. Protect nests from livestock to reduce trampling 5.62. Mark fences to reduce bird collision mortality 5.63. Create open patches or strips in permanent grassland

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46 46 55 57 59 63 64 64 65 65 66 67 67 68 68 69 69 73 73 73 75 76 76 78 81 81 83 84 85 85 87 87 88 90 93 93 94 95 96 97 97 98 99 100 100 100 100 100 103 103 104

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Contents

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Perennial, non-timber crops 5.64. Maintain traditional orchards 5.65. Manage perennial bioenergy crops to benefit wildlife

104 105 105

Aquaculture 5.66. Reduce conflict with humans to reduce persecution 5.67. Scare birds from fish farms 5.68. Disturb birds at roosts 5.69. Use electric fencing to exclude fish-eating birds 5.70. Use netting to exclude fish-eating birds 5.71. Disturb birds using foot patrols 5.72. Use ‘mussel socks’ to prevent birds from attacking shellfish 5.73. Translocate birds away from fish farms 5.74. Increase water turbidity to reduce fish predation by birds 5.75. Provide refuges for fish within ponds 5.76. Use in-water devices to reduce fish loss from ponds 5.77. Spray water to deter birds from ponds 5.78. Deter birds from landing on shellfish culture gear

106 106 106 109 110 111 112 112 113 113 114 114 115 115

6. Threat: Energy production and mining Key messages 6.1. Paint wind turbines to increase their visibility

117 117 117

7. Threat: Transportation and service corridors Key messages – Verges and airports Key messages – Power lines and electricity pylons

118 118 118

Verges and airports 7.1. Mow roadside verges 7.2. Sow roadside verges 7.3. Scare or otherwise deter birds from airports

119 119 119 119

Power lines and electricity pylons 7.4. Bury or isolate power lines to reduce incidental mortality 7.5. Remove earth wires to reduce incidental mortality 7.6. Thicken earth wire to reduce incidental mortality 7.7. Mark power lines to reduce incidental mortality 7.8. Use raptor models to deter birds and so reduce incidental mortality 7.9. Add perches to electricity pylons to reduce electrocution 7.10. Insulate power pylons to prevent electrocution 7.11. Use perch-deterrents to stop raptors perching on pylons 7.12. Reduce electrocutions by using plastic, not aluminium, leg rings to mark birds

120 120 121 121 121 124 124 125 125

8. Threat: Biological resource use Key messages – reducing exploitation and conflict Key messages – reducing fisheries bycatch Reducing exploitation and conflict 8.1. Use legislative regulation to protect wild populations 8.2. Increase ‘on-the-ground’ protection to reduce unsustainable levels of exploitation 8.3. Promote sustainable alternative livelihoods 8.4. Use education programmes and local engagement to help reduce persecution or exploitation of species 8.5. Employ local people as ‘biomonitors’

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9.

Contents 8.6. Mark eggs to reduce their appeal to egg collectors 8.7. Relocate nestlings to reduce poaching 8.8. Use wildlife refuges to reduce hunting disturbance 8.9. Introduce voluntary ‘maximum shoot distances’ 8.10. Provide ‘sacrificial’ grasslands to reduce the impact of wild geese on crops 8.11. Move fish-eating birds to reduce conflict with fishermen 8.12. Scare fish-eating birds from areas to reduce conflict

136 136 137 138 138 139 139

Reduce fisheries bycatch 8.13. Set longlines at night to reduce seabird bycatch 8.14. Turn deck lights off during night-time setting of longlines to reduce bycatch 8.15. Use streamer lines to reduce seabird bycatch on longlines 8.16. Use larger hooks to reduce seabird bycatch 8.17. Use a water cannon when setting longlines to reduce seabird bycatch 8.18. Set lines underwater to reduce seabird bycatch 8.19. Set longlines at the side of the boat to reduce seabird bycatch 8.20. Use a line shooter to reduce seabird bycatch 8.21. Use bait throwers to reduce seabird bycatch 8.22. Tow buoys behind longlining boats to reduce seabird bycatch 8.23. Dye baits to reduce seabird bycatch 8.24. Use high-visibility longlines to reduce seabird bycatch 8.25. Use a sonic scarer when setting longlines to reduce seabird bycatch 8.26. Weight baits or lines to reduce longline bycatch of seabirds 8.27. Use shark liver oil to deter birds when setting lines 8.28. Thaw bait before setting lines to reduce seabird bycatch 8.29. Reduce seabird bycatch by releasing offal overboard when setting longlines 8.30. Use bird exclusion devices such as ‘Brickle curtains’ to reduce seabird mortality when hauling longlines 8.31. Use acoustic alerts on gillnets to reduce seabird bycatch 8.32. Use high-visibility mesh on gillnets to reduce seabird bycatch 8.33. Reduce gillnet deployment time to reduce seabird bycatch 8.34. Mark trawler warp cables to reduce seabird collisions 8.35. Reduce ‘ghost fishing’ by lost/discarded gear 8.36. Reduce bycatch through seasonal or area closures

139 140

Threat: Human intrusions and disturbance Key messages 9.1. Use wildlife refuges to reduce hunting disturbance 9.2. Use signs and access restrictions to reduce disturbance at nest sites 9.3. Set minimum distances for approaching birds (buffer zones) 9.4. Provide paths to limit the extent of disturbance 9.5. Reduce visitor group sizes 9.6. Use voluntary agreements with local people to reduce disturbance 9.7. Start educational programmes for personal watercraft owners 9.8. Habituate birds to human visitors 9.9. Use nest covers to reduce the impact of research on predation of ground-nesting seabirds

10. Threat: Natural system modifications Key messages 10.1. Use prescribed burning 10.2. Use fire suppression/control

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Contents 10.3. 10.4. 10.5. 10.6. 10.7. 10.8. 10.9. 10.10. 10.11. 10.12. 10.13. 10.14. 10.15. 10.16. 10.17. 10.18. 10.19. 10.20. 10.21. 10.22. 10.23. 10.24. 10.25. 10.26. 10.27. 10.28.

Protect nest trees before burning Clear or open patches in forests Clearcut and re-seed forests Thin trees within forests Coppice trees Use patch retention harvesting instead of clearcutting Use selective harvesting/logging instead of clearcutting Use variable retention management during forestry operations Use shelterwood cutting instead of clearcutting Manage woodland edges for birds Manually control or remove mid-storey and ground-level vegetation (including mowing, chaining, cutting etc) Replace non-native species of tree/shrub Provide deadwood/snags in forests Remove coarse woody debris from forests Apply herbicide to mid- and under-storey vegetation Treat wetlands with herbicide Employ grazing in natural and semi-natural habitats Plant trees to act as windbreaks Re-seed grasslands Fertilise artificial grasslands Raise water levels in ditches or grassland Manage water level in wetlands Use environmentally sensitive flood management Use greentree reservoir management Plough habitats Create scrapes and pools in wetlands and wet grasslands

ix 184 184 186 187 189 190 191 192 193 193 194 202 202 204 205 206 208 214 215 215 217 218 220 220 221 222

11. Habitat restoration and creation Key messages 11.1. Restore or create forests 11.2. Restore or create grasslands 11.3. Restore or create traditional water meadows 11.4. Restore or create shrubland 11.5. Restore or create savannas 11.6. Restore or create wetlands and marine habitats

224 224 225 229 235 236 237 237

12. Threat: Invasive alien and other problematic species Key messages – reduce predation by other species Key messages – reduce incidental mortality during predator eradication or control Key messages – reduce nest predation by excluding predators from nests or nesting areas Key messages – reduce mortality by reducing hunting ability or changing predator behaviour Key messages – reduce competition with other species for food and nest sites Key messages – reduce adverse habitat alteration by other species Key messages – reduce parasitism and disease Key messages – reduce detrimental impacts of other problematic species

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Reduce predation by other species 12.1. Remove or control predators to enhance bird populations and communities

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Contents Predator control on islands 12.2. Control avian predators on islands 12.3. Control mammalian predators on islands 12.4. Control invasive ants on islands 12.5. Control predators not on islands 12.6. Reduce predation by translocating predators

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Reduce incidental mortality during predator eradication or control 12.7. Do birds take bait designed for pest control? 12.8. Distribute poison bait using dispensers 12.9. Use repellents on baits 12.10. Use coloured baits to reduce accidental mortality during predator control

270 270 271 271

Reduce nest predation by excluding predators from nests or nesting areas 12.11. Physically protect nests from predators using non-electric fencing 12.12. Protect bird nests using electric fencing 12.13. Physically protect nests with individual exclosures/barriers or provide shelters for chicks 12.14. Can nest protection increase nest abandonment? 12.15. Can nest protection increase predation of adults and chicks? 12.16. Use artificial nests that discourage predation 12.17. Use multiple barriers to protect nests 12.18. Plant nesting cover to reduce nest predation 12.19. Use snakeskin to deter mammalian nest predators 12.20. Use mirrors to deter nest predators 12.21. Use naphthalene to deter mammalian predators 12.22. Use ultrasonic devices to deter cats 12.23. Protect nests from ants 12.24. Guard nests to prevent predation 12.25. Use ‘cat curfews’ to reduce predation 12.26. Use lion dung to deter domestic cats 12.27. Play spoken-word radio programmes to deter predators

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Reduce mortality by reducing hunting ability or changing predator behaviour 12.28. Use collar-mounted devices to reduce predation 12.29. Use supplementary feeding to reduce predation 12.30. Use aversive conditioning to reduce nest predation 12.31. Reduce predation by translocating nest boxes Reduce competition with other species for food and nest sites 12.32. Reduce inter-specific competition for nest sites by removing competitor species 12.33. Reduce inter-specific competition for nest sites by modifying habitats to exclude competitor species 12.34. Protect nest sties from competitors 12.35. Reduce competition between species by providing nest boxes 12.36. Reduce inter-specific competition for food by removing or controlling competitor species Reduce adverse habitat alteration by other species 12.37. Reduce adverse habitat alterations by excluding problematic species 12.38. Control or remove habitat-altering mammals 12.39. Remove problematic vegetation 12.40. Use buffer zones to reduce the impact of invasive plant control

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Reduce detrimental impacts of other problematic species 12.49. Use copper strips to exclude snails from nests

317 317

13. Threat: Pollution Key messages – Industrial pollution Key messages – Agricultural pollution Key message – Air-borne pollutants Key messages – Excess energy

316 317

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Industrial pollution 13.1. Clean birds following oil spills 13.2. Relocate birds following oil spills 13.3. Deter or prevent birds from landing on toxic pools 13.4. Use repellents to deter birds from landing on pools polluted by mining

320 320 322 323 325

Agricultural pollution 13.5. Reduce pesticide or herbicide use generally 13.6. Restrict certain pesticides or other agricultural chemicals 13.7. Provide food for vultures to reduce mortality from diclofenac 13.8. Make selective use of spring herbicides 13.9. Use organic rather than mineral fertilisers 13.10. Reduce chemical inputs in permanent grassland management 13.11. Leave headlands in fields unsprayed (conservation headlands) 13.12. Provide unfertilised cereal headlands in arable fields 13.13. Plant riparian buffer strips 13.14. Provide buffer strips around in-field ponds

325 325 327 328 329 329 329 330 332 332 333

Air-borne pollutants 13.15. Use lime to reduce acidification in lakes

333 333

Excess energy 13.16. Reduce incidental mortality from birds being attracted to artificial lights 13.17. Turn off lights to reduce mortality from artificial lights 13.18. Reduce the intensity of lighthouse beams 13.19. Shield lights to reduce mortality from artificial lights 13.20. Use flashing lights to reduce mortality from artificial lights 13.21. Use lights low in spectral red to reduce mortality from artificial lights 13.22. Use volunteers to collect downed birds and rehabilitate them

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14. Threat: Climate change, extreme weather and geological events Key messages 14.1. Water nesting mounds to increase incubation success in malleefowl 14.2. Replace nesting substrate following severe weather

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Reduce parasitism and disease 12.41. Remove/treat endoparasites and diseases 12.42. Exclude or control ‘reservoir species’ to reduce parasite burdens 12.43. Remove/treat ectoparasites to increase survival or reproductive success 12.44. Guard nests to reduce risk of ectoparasites 12.45. Remove/control brood parasites 12.46. Use false brood parasite eggs to discourage brood parasitism 12.47. Provide supplementary food to increase parental presence and so reduce brood parasitism 12.48. Alter artificial nest sites to discourage brood parasitism

333 334 334 334 335 335 336 337 337 337 338

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15. General responses to small/declining populations Key messages – inducing breeding, rehabituation and egg removal Key messages – provide artificial nesting sites Key messages – foster chicks in the wild Key messages – provide supplementary food Key messages – translocations

339 339 339 340 341 342

15.1.

Use artificial visual and auditory stimuli to induce breeding in wild populations 15.2. Rehabilitate injured birds 15.3. Remove eggs from wild nests to increase reproductive output 15.4. Provide artificial nesting sites 15.5. Clean nest boxes to increase occupancy or reproductive success 15.6. Use differently-coloured artificial nests 15.7. Provide nesting material for wild birds 15.8. Repair/support nests to support breeding 15.9. Artificially incubate eggs or warm nests 15.10. Provide nesting habitat for birds that is safe from extreme weather 15.11. Remove vegetation to create nesting areas 15.12. Guard nests to increase nest success

343 343 344 345 390 392 393 393 394 394 395 397

Foster chicks in the wild 15.13. Foster eggs or chicks with wild conspecifics 15.14. Foster eggs or chicks with wild non-conspecifics (cross-fostering)

398 398 404

Provide supplementary food 15.15. Provide supplementary food to increase reproductive success 15.16. Provide supplementary food to allow the rescue of a second chick 15.17. Provide supplementary food to increase adult survival 15.18. Can supplementary feeding increase predation or parasitism? 15.19. Provide supplementary food through the establishment of food populations 15.20. Use perches to increase foraging success 15.21. Place feeders close to windows to reduce collisions 15.22. Provide supplementary water to increase survival or reproductive success 15.23. Provide calcium supplements to increase survival or reproductive success

407 408 430 431 449

Translocations 15.24. Translocate birds to re-establish populations or increase genetic variation 15.25. Use techniques to increase the survival of species after capture 15.26. Ensure translocated birds are familiar with each other before release 15.27. Ensure genetic variation to increase translocation success 15.28. Translocate nests to avoid disturbance 15.29. Use vocalisations to attract birds to new sites 15.30. Use decoys to attract birds to new sites 15.31. Alter habitat to encourage birds to leave an area

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16. Captive breeding, rearing and releases (ex situ conservation) Key messages – captive breeding Key messages – release of captive-bred individuals

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Release of captive-bred individuals 16.8. Release captive-bred individuals into the wild to restore or augment wild populations 16.9. Use appropriate populations to source released populations 16.10. Use holding pens at release sites 16.11. Clip birds’ wings on release 16.12. Release birds in groups 16.13. Release chicks and adults in ‘coveys’ 16.14. Release birds as adults or sub-adults, not juveniles 16.15. Use ‘anti-predator training’ to improve survival after release 16.16. Use ‘flying training’ before release 16.17. Provide supplementary food during and after release 16.18. Use microlites to help birds migrate

505

Index

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Captive breeding 16.1. Use captive breeding to increase or maintain populations 16.2. Can captive breeding have deleterious effects on individual fitness? 16.3. Use artificial insemination in captive breeding 16.4. Freeze semen for use in artificial insemination 16.5. Wash contaminated semen and use it for artificial insemination 16.6. Artificially incubate and hand-rear birds in captivity 16.7. Use puppets to increase the success of hand-rearing

505 520 521 523 524 524 525 527 528 529 530 531

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Advisory board We thank the following people for advising on the scope and content of this synopsis: Dr Andrew Brown, Natural England Dr David Gibbons, Royal Society for the Protection of Birds Dr Roger Mitchell, Natura International Dr Jörn Scharlemann, UNEP-World Conservation Monitoring Centre Dr Gavin Siriwardena, British Trust for Ornithology Dr Alison Stattersfield, BirdLife International Dr David Stroud, Joint Nature Conservation Committee Professor Des Thompson, Scottish Natural Heritage

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About the authors David Williams is a Doctoral Student in the Department of Zoology, University of Cambridge. Robert G. Pople is a former Research Assistant in the Department of Zoology, University of Cambridge. David A. Showler is a Research Associate in the School of Biological Sciences, University of East Anglia and the Department of Zoology, University of Cambridge. Lynn Dicks is a Research Associate in the Department of Zoology, University of Cambridge. Matthew F. Child is a Research Assistant in the Department of Zoology, University of Cambridge. Erasmus K. H. J. zu Ermgassen is a Student in the Department of Veterinary Medicine, University of Cambridge. William J. Sutherland is the Miriam Rothschild Professor of Conservation Biology at the University of Cambridge.

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Acknowledgements This synopsis was funded by the Natural Environment Research Council and Arcadia. We would also like to thank Dr Stephanie Prior for providing support throughout the project and all the people who gave help and advice and allowed us access to their research: Helen Baker (Joint Nature Conservation Committee), Leon Bennun (BirdLife International), Mark Bolton (Royal Society for the Protection of Birds, RSPB), Chris Bowden (RSPB), Jöel Bried (University of the Azores), Rhys Bullman (Scottish Nature Conservancy), Bob Carling (Pelagic Publishing), Motti Charter (Tel Aviv University), Mariano Codesido (University of Buenos Aires), James Dwyer (Virginia Tech), Rob Field (RSPB), Graham Fulton (Edith Cowan University), Emma Gyuris (James Cook University), Wendy Johnson (Hawaii Audubon Society), Tim Johnson (UNEP – World Conservation Monitoring Centre), Naoki Katayama (University of Tokyo), Andrew Kelly (Royal Society for the Prevention of Cruelty to Animals), Will Kirby (RSPB), Raivo Mänd (University of Tartu), Nigel Massen (Pelagic Publishing), Marcos Moleón Páiz (University of Granada), Roberto Muriel (Consejo Superior de Investigaciones Cientificas), Itziar Olmedo (University of Cambridge), Ray Poulin (Royal Saskatchewan Museum), David Priddel (Department of Environment, Climate Change and Water, New South Wales), Casey Primacio (Hawaii Audubon Society), C. John Ralph (US Department of Agriculture Forest Service), Michel Robert (Canadian Wildlife Service), Maurizio Sarà (University of Palermo), Debbie Saunders (Australian National University), Phil Seddon (University of Otago), Danaë Sheehan (RSPB), Jennifer Smart (RSPB), Ian Smales (Biosis Research), John Smallwood (Montclair State University), Juliet Vickery (British Trust for Ornithology) and Matt Wagner (Texas Parks and Wildlife Department).

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1.

About this book

The purpose of Conservation Evidence synopses Conservation Evidence synopses do

Conservation Evidence synopses do not

• Bring together scientific evidence captured by the Conservation Evidence project (over 3,000 studies so far) on the effects of interventions to conserve biodiversity

• Include evidence on the basic ecology of species or habitats, or threats to them

• List all realistic interventions for the species group or habitat in question, regardless of how much evidence for their effects is available

• Make any attempt to weight or prioritise interventions according to their importance or the size of their effects

• Describe each piece of evidence, including methods, as clearly as possible, allowing readers to assess the quality of evidence

• Weight or numerically evaluate the evidence according to its quality

• Work in partnership with conservation practitioners, policymakers and scientists to develop the list of interventions and ensure we have covered the most important literature

• Provide answers to conservation problems. We provide scientific information to help with decision-making

Who is this synopsis for? If you are reading this, we hope you are someone who has to make decisions about how best to support or conserve biodiversity. You might be a land manager, a conservationist in the public or private sector, a farmer, a campaigner, an advisor or consultant, a policymaker, a researcher or someone taking action to protect your own local wildlife. Our synopses summarise scientific evidence relevant to your conservation objectives and the actions you could take to achieve them. We do not aim to make your decisions for you, but to support your decision-making by telling you what evidence there is (or isn’t) about the effects that your planned actions could have. When decisions have to be made with particularly important consequences, we recommend carrying out a systematic review, as the latter is likely to be more comprehensive than the summary of evidence presented here. Guidance on how to carry out systematic reviews can be found from the Centre for Evidence-Based Conservation at the University of Bangor (www.cebc.bangor.ac.uk).

The Conservation Evidence project The Conservation Evidence project has three parts: An online, open access journal Conservation Evidence publishes new pieces of research on the effects of conservation management interventions. All our papers are written by, or in conjunction with, those who carried out the conservation work and include some monitoring of its effects.

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2

About this book

An ever-expanding database of summaries of previously published scientific papers, reports, reviews or systematic reviews that document the effects of interventions. Synopses of the evidence captured in parts one and two on particular species groups or habitats. Synopses bring together the evidence for each possible intervention. They are freely available online and available to purchase in printed book form. These resources currently comprise over 3,000 pieces of evidence, all available in a searchable database on the website www.conservationevidence.com. Alongside this project, the Centre for Evidence-Based Conservation (www.cebc.bangor. ac.uk) and the Collaboration for Environmental Evidence (www.environmentalevidence.org) carry out and compile systematic reviews of evidence on the effectiveness of particular conservation interventions. These systematic reviews are included on the Conservation Evidence database. Of the 322 bird conservation interventions identified in this synopsis, five are the subjects of current systematic reviews: • How does the impact of grazing on heathland compare with the impact of burning, cutting or no management? http://www.environmentalevidence.org/SR14.html • Is predator control an effective strategy for enhancing bird populations? http://www. environmentalevidence.org/SR38.html. • Do matrix features affect species movement? http://www.environmentalevidence.org/ SR43.html • Does structural connectivity facilitate dispersal of native species in Australia’s fragmented terrestrial landscape? http://www.environmentalevidence.org/SR44.html • How do thinning and burning treatments in south-western conifer forests in the United States affect wildlife distribution, abundance and population performance? http://www. environmentalevidence.org/SR66.html In addition, three systematic reviews provide important information on the impacts of threats on bird populations: • Effects of wind turbines on bird abundance. http://www.environmentalevidence.org/ SR4.html • What is the impact of public access on the breeding success of ground-nesting and cliffnesting birds? http://www.environmentalevidence.org/SR16.html • What are the impacts of human recreational activity on the distribution, nest-occupancy rates and reproductive success of breeding raptors? http://www.environmentalevidence. org/SR27.html Another provides evidence for how to apply an intervention: • Do trapping interventions effectively reduce or eradicate populations of the American mink (Mustela vison)? http://www.environmentalevidence.org/SR7.html. There are several interventions which we feel would benefit significantly from systematic reviews: • • • •

Interventions to reduce the impact of electricity pylons and power lines Interventions to reduce seabird bycatch The provision of artificial nest sites The provision of supplementary food

Scope of the Bird Conservation synopsis This synopsis covers evidence for the effects of conservation interventions for native (see below), wild birds.

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About this book

3

It is restricted to evidence captured on the website www.conservationevidence.com. It includes papers published in the journal Conservation Evidence, evidence summarised on our database and systematic reviews collated by the Collaboration for Environmental Evidence. We have gathered evidence from all around the world, and the apparent over (or underrepresentation) of some regions reflects the current biases in published research papers available to Conservation Evidence.

Native vs. non-native species This synopsis does not include evidence from the substantial literature on husbandry of domestic birds, or non-native gamebirds (e.g. common pheasants Phasianus colchicus in Europe and North America). However, where these interventions affect native species, or are relevant to the conservation of native, wild species, they are included (e.g. management of farmland for common pheasants has a significant impact on several declining native songbirds in the UK, see Stoate (2002) in ‘Manage hedges to benefit wildlife’, ‘Plant nectar flower mixture/wildflower strips’, ‘Plant wild bird seed cover strips’, ‘Provide supplementary food for birds’, ‘Create beetle banks’, ‘Control predators not on islands – songbirds’, ‘Reduce pesticide or herbicide use generally’.

How we decided which conservation interventions to include Our list of interventions has been agreed in partnership with an Advisory Board made up of international conservationists and academics with expertise in bird conservation. Although the list of interventions may not be exhaustive, we have tried to include all actions that have been carried out or advised to support populations or communities of wild birds.

How we reviewed the literature In addition to evidence already captured by the Conservation Evidence project, we have searched the following sources for evidence relating to bird conservation: • Fifteen specialist bird conservation journals, from their first publication to the end of 2010 (African Bird Club Bulletin, The Auk, Bird Conservation International, Bird Study, BTO Research Reports, Emu, Ibis, Journal of Avian Biology – formerly Ornis Scandinavica, Journal of Field Ornithology, Journal Raptor Research – formerly Raptor Research, Ornitologia Neotropical, RSPB Research Reports, The Condor, Waterbirds – formerly Colonial Waterbirds, Wilson Journal of Ornithology – formerly Wilson Bulletin) • Twenty general conservation journals over the same time period. • Where we knew of an intervention which we had not captured evidence for, we performed keyword searches on ISI Web of Science and www.scholar.google.com for this intervention. Individual studies covered in this synopsis are all included in full or in summary on the Conservation Evidence website. The criteria for inclusion of studies in the Conservation Evidence database are as follows: • There must have been an intervention that conservationists would do • Its effects must have been monitored quantitatively In some cases, where a body of literature has strong implications for conservation of a particular species group or habitat, although it does not directly test interventions for their effects, we refer the reader to this literature, but present no evidence.

How the evidence is summarised Conservation interventions are grouped primarily according to the relevant direct threats, as defined in the International Union for the Conservation of Nature (IUCN)’s Unified

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Classification of Direct Threats (www.iucnredlist.org/technical-documents/classificationschemes/habitats-classification-scheme-ver3). In most cases, it is clear which main threat a particular intervention is meant to alleviate or counteract. Not all IUCN threat types are included, only those that threaten birds, and for which realistic conservation interventions have been suggested. Some important interventions can be used in response to many different threats, and it would not make sense to split studies up depending on the specific threat they were studying. We have therefore separated out these interventions, following the IUCN’s Classification of Conservation Actions (http://www.iucnredlist.org/technical-documents/classificationschemes/conservation-actions-classification-scheme-ver2). The actions we have separated out are: ‘Habitat protection’, ‘Education and community development’, ‘Habitat restoration and creation’, ‘General responses to small/declining populations’ and ‘Captive breeding, rearing and releases (ex situ conservation)’. These respectively match the following IUCN categories: ‘Land/water protection’, ‘Education and awareness’ and ‘Livelihood, economic and other incentives’, ‘Land/water management – Habitat and natural process restoration’, and ‘Species Management’. Normally, no intervention is listed in more than one place, and when there is ambiguity about where a particular intervention should fall there is clear cross-referencing. Some studies describe the effects of multiple interventions. When this is the case, cross-referencing is again used to direct readers to the other interventions investigated. Where a study has not separated out the effects of different interventions, the study is only described once, but readers are directed to it from the other interventions. In the text of each section, studies are presented in chronological order, so the most recent evidence is presented at the end. The summary text at the start of each section groups studies according to their findings. At the start of each chapter, a series of key messages provides a rapid overview of the evidence. These messages are condensed from the summary text for each intervention. Background information is provided where we feel recent knowledge is required to interpret the evidence. This is presented separately and relevant references included in the reference list at the end of each intervention section. References containing evidence for the effects of interventions are summarised in more detail on the Conservation Evidence website. In electronic versions of the synopsis, they are hyperlinked directly to the summary. If you do not have access to the electronic version of the synopsis, searching for the reference details or the species name on www.conservationevidence.com is the quickest way to locate summaries. The information in this synopsis is available in three ways: • As a book, printed by Pelagic Publishing and for sale from www.nhbs.com • As a pdf to download from www.conservationevidence.com • As text for individual interventions on the searchable database at www.conservationevidence.com.

Terminology used to describe evidence Unlike systematic reviews of particular conservation questions, we do not quantitatively assess the evidence, or weight it according to quality. However, to allow you to interpret evidence, we make the size and design of each trial we report clear. The table below defines the terms that we have used to do this. The strongest evidence comes from randomised, replicated, controlled trials with pairedsites and before and after monitoring.

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Term

Meaning

Site comparison

A study that considers the effects of interventions by comparing sites that have historically had different interventions or levels of intervention.

Replicated

The intervention was repeated on more than one individual or site. In conservation and ecology, the number of replicates is much smaller than it would be for medical trials (when thousands of individuals are often tested). If the replicates are sites, pragmatism dictates that between five and ten replicates is a reasonable amount of replication, although more would be preferable. We provide the number of replicates wherever possible, and describe a replicated trial as ‘small’ if the number of replicates is small relative to similar studies of its kind.

Controlled

Individuals or sites treated with the intervention are compared with control individuals or sites not treated with the intervention.

Paired sites

Sites are considered in pairs, within which one was treated with the intervention and the other was not. Pairs of sites are selected with similar environmental conditions, such as soil type or surrounding landscape. This approach aims to reduce environmental variation and make it easier to detect a true effect of the intervention.

Randomised

The intervention was allocated randomly to individuals or sites. This means that the initial condition of those given the intervention is less likely to bias the outcome.

Before-and-after trial

Monitoring of effects was carried out before and after the intervention was imposed.

Review

A conventional review of literature. Generally, these have not used an agreed search protocol or quantitative assessments of the evidence.

Systematic review

A systematic review follows an agreed set of methods for identifying studies and carrying out a formal ‘meta-analysis’. It will weight or evaluate studies according to the strength of evidence they offer, based on the size of each study and the rigour of its design. All environmental systematic reviews are available at: www.environmentalevidence.org/ index.htm

Taxonomy We have followed the taxonomy used in BirdLife International’s 2011 checklist (http://www. birdlife.org/datazone/info/taxonomy), updating the names used in original papers where necessary. We have always referred to the species name used in the original paper as well. Where possible, common names and Latin names are both given the first time each species is mentioned within each intervention. Where interventions have a large literature associated with them we have sometimes divided studies along taxonomic or functional lines. These do not follow strict taxonomic divisions, but instead are designed to maximise their utility. For example, storks, herons and ibises are often included together as both groups are large wading birds and may respond to interventions in similar ways.

Habitats Where interventions have a large literature associated with them and effects could vary between habitats, we have divided the literature using the IUCN Habitat Classification Scheme (Version 3.0), available from www.iucnredlist.org.

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Significant results Throughout the synopsis we have quoted results from papers. Unless specifically stated, these results reflect statistical tests performed on the results.

Multiple interventions Many studies investigate several interventions at once. When the effects of different interventions are separated, then the results are discussed separately in the relevant sections. However, often the effects of multiple interventions cannot be separated. When this is the case, the study is included in the section on each intervention, but the fact that several interventions were used is highlighted.

How you can help to change conservation practice If you know of evidence relating to bird conservation that is not included in this synopsis, we invite you to contact us, via the www.conservationevidence.com website. Following guidelines provided on the site, you can submit a summary of a previously published study, or submit a paper describing new evidence to the Conservation Evidence journal. We particularly welcome summaries written by the authors of papers published elsewhere, and papers submitted by conservation practitioners.

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2.

Habitat protection

Habitat destruction is the largest single threat to biodiversity, and the spread of agriculture into natural habitats alone threatens 1,065 species of birds (87% of all threatened species) (BirdLife International 2008). Habitat protection is therefore one of the most frequently used conservation interventions, particularly in the tropics and in other areas with large areas of surviving natural vegetation. Habitat protection can be through the designation of legally protected areas (PAs), using national or local laws; through the designation of Important Bird Areas (IBAs) or similar schemes, which, whilst providing no formal protection, may increase the profile of a site and make its conversion more difficult; or through the protection of entire habitat types, for example through the EU’s Habitats Directive. However, it can be difficult to measure the effectiveness of such areas: there may be no suitable controls; monitoring often only begins with the designation of the PA and PAs tend to be located in areas that would be less likely to be cleared even if it was not protected, making the prevention of agricultural expansion less politically difficult (Joppa & Pfaff 2011). Analysis of PAs often, therefore, requires large datasets, and this means that most studies investigating them use either satellite imagery (e.g. Joppa et al. 2008) or overall ‘condition’ scores (e.g. Mwangi et al. 2010), rather than data on bird populations, which are much harder to collect. It is worth noting that the designation of a habitat or area as ‘protected’ (also known as de jure protection) does not necessarily mean protection in practical terms (de facto protection). The chapter on ‘Threat: Biological resource use’ contains several studies that examine the effect of greater de facto protection on bird populations. Birdlife International (2008) State of the world’s birds: Indicators for our changing world. Birdlife International. Joppa, L. N., Loarie, S. R. & Pimm, S. L. (2008) On the protection of ‘protected areas.’ Proceedings of the National Academy of Sciences, 105, 6673 – 6678. Joppa, L.N. & Pfaff, A. (2011) Global protected area impacts. Proceedings of the Royal Society B: Biological Sciences, 278, 1633 –1638. Mwangi, M. A. K., Butchart, S. H. M., Munyekenye, F. B., Bennun, L. A., Evans, M. I., Fishpool, L. D. C., Kanyanya, E., Madindou, I., Machekele, J., Matiku, P., Mulwa, R., Ngari, A., Siele, J. & Stattersfield, A. J. (2010) Tracking trends in key sites for biodiversity: a case study using Important Bird Areas in Kenya. Bird Conservation International, 20, 215 –230.

Key messages Legally protect habitats Four studies from Europe found that populations increased after habitat protection and a review from China found high use of protected habitats by cranes. A replicated, randomised and controlled study from Argentina found that some, but not all bird groups had higher species richness or were at higher densities in protected habitats.

Ensure connectivity between habitat patches Two studies of a replicated, controlled experiment in Canadian forests found that some species (not forest specialists) were found at higher densities in forest patches connected to continuous forest, compared to isolated patches and that some species used corridors more than clearcuts between patches.

Provide or retain un-harvested buffer strips Three replicated studies from the USA found that species richness or abundances were higher in narrow (100 years) than in a woodland selectively logged for Celtis tala until 1960. Insecteating bird density and species richness was higher in the protected woodland than in the exploited woodland and fruit-eating birds showed higher total density in the protected woodland in spring and summer but species richness was similar between both woodland types. There were no differences between sites for seed-eating birds. A replicated study in 1997 in 19 nature reserves across England (4) found that they held consistently higher densities of northern lapwing Vanellus vanellus, common redshank Tringa totanus and common snipe Gallinago gallinago than the non-reserve Environmentally Sensitive Areas (an agri-environment scheme designation) surrounding them (densities approximately 730% higher for lapwing, 520% higher for redshank and 1600% higher for snipe). In addition, population trends were generally positive in reserves (except for snipe), but negative outside them (lapwing: 0.9 –7.4% annual increase inside reserves vs. 0.7–13% decline outside; redshank: 3.9 – 8.6% increase vs. 1.8 –18.6% decrease; snipe: 6.1–16.8% decrease in reserves vs. 7.3 –29.7% decrease outside). The authors note that snipe have declined by approximately 70% across all reserves, due mainly to declines at a single reserve with a large population and on reserves with mineral soils (i.e. those with little organic matter). However, declines outside reserves were considerably higher than those on reserves (20% vs. 10% annually). This study is discussed in detail in ‘Pay farmers to cover the costs of conservation measures’ and ‘Maintain traditional water meadows’. A controlled, before-and-after study from 1970 –2000 across Europe (5) found that targeted species in European Union (EU) countries, which were legally obliged to increase coverage of special protected areas (SPAs), had significantly more positive population trends after implementation of the directive and compared to non-EU countries (no implementation). Statistical models suggested that for every additional 1% increase in SPA area, the chances of all species experiencing positive population growth increased by 4%, with a 7% increase for

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target species. The authors argue that the stronger response of the target species provides direct evidence for the effectiveness of the EU Bird (79/409/EEC, est. 1979) and Habitats (92/43/EEC, est. 1992) Directives. Although non-target species’ trends did not differ between EU and non-EU countries there was some evidence that these populations were more positive in EU countries with more extensive SPA networks. A 2007 site comparison study of 677 plots covering 38,705 ha across southern England (6) found that for three wader species, population trends were most favourable in nature reserves, compared with farmland under the Environmentally Sensitive Areas scheme. Between 1982 and 2002, common redshank Tringa totanus declined by 70% in the wider countryside but increased by 160% in nature reserves outside Environmentally Sensitive Areas. Northern lapwing Vanellus vanellus showed a 48% decline in the wider countryside, and increased only in nature reserves outside Environmentally Sensitive Areas (by 55%) and reserves with Environmentally Sensitive Area enhancement (121%). Common snipe Gallinago gallinago breeding numbers decreased everywhere (commonly with declines of 90% or more), although declines were smaller in nature reserves outside Environmentally Sensitive Areas (−66%) and reserves in Environmentally Sensitive Area enhancement (−24%). (1) Donazar, J. A. (1990) Population trends of the griffon vulture Gyps fulvus in northern Spain between 1969 and 1989 in relation to conservation measures. Biological Conservation, 53, 83 –91. (2) Davis, C. (1998) A review of the success of major crane conservation techniques. Bird Conservation International, 8, 19 –30. (3) Cueto, V. R. & Casenave, J. L. D. (2000) Bird assemblages of protected and exploited coastal woodlands in east-central Argentina. The Wilson Bulletin, 112, 395 – 402. (4) Ausden, M. & Hirons, G. J. M. (2002) Grassland nature reserves for breeding wading birds in England and the implications for the ESA agri-environment scheme. Biological Conservation, 106, 279 –291. (5) Donald, P. F., Sanderson, F. J., Burfield, I. J., Bierman, S. M., Gregory, R. D. & Waliczky, Z. (2007) International conservation policy delivers benefits for birds in Europe. Science, 317, 810 – 813. (6) Wilson, A., Vickery, J. & Pendlebury, C. (2007) Agri-environment schemes as a tool for reversing declining populations of grassland waders: mixed benefits from Environmentally Sensitive Areas in England. Biological Conservation, 136, 128 –135.

2.2.

Ensure connectivity between habitat patches

• A replicated, controlled study in Canada (2) found significantly higher abundances of some birds, but not forest specialists, in forest patches connected to a continuous area of forest, than in isolated patches. • Another study of the same system (1) found evidence that corridors were used by some bird species more than clearcuts between patches, although corridors near cut forest were not used more than those near uncut stands.

Background Habitat fragmentation, as well as destruction, may be an important driver of population declines. Small areas hold fewer species than large ones and if individuals are unable to cross areas of converted habitat then populations in separate habitat patches will become isolated. This potentially makes them more vulnerable to extinction, from natural variations in birth and death rates or sex ratios; from inbreeding depression and from outside pressures, both natural (such as storms or wildfires) and man-made (such as hunting or continued habitat loss), although the precise effects of habitat fragmentation, as opposed to loss, are debated (e.g. Fahrig 1997). Theoretically, the number of species surviving in a habitat fragment is determined by its size and its effective distance to other habitat patches (MacArthur & Wilson 1967). Connecting remaining areas of habitat is therefore often seen as a way to increase the viability of populations, but there is considerable debate as to the effectiveness of such ‘wildlife corridors’ (e.g. Beier & Noss 1998).

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Studies describing the effects of creating habitat corridors, rather than retaining them are described in ‘Habitat restoration and creation’. Beier, P. & Noss, R. F. (1998) Do habitat corridors provide connectivity? Conservation Biology, 12, 1241–1252. Fahrig, L. (1997) Relative effects of habitat loss and fragmentation on population extinction. The Journal of Wildlife Management, 61, 603 – 610. MacArthur, R. H. & Wilson, E. O. (1967) The Theory of Island Biogeography. Princeton University Press, Princeton, N.J.

A replicated, controlled study in boreal forests in 1993–5 in Alberta, Canada (1), found that significantly higher abundances of the ten most common under-storey birds were found in three riparian corridors between forest patches than in three clearcuts between patches. Only two of the ten were found nesting or foraging in clearcuts. In addition, significantly more juveniles used corridors following logging, than before, but only in one site. No more birds used the buffer strips near logged forest than similar strips near un-logged forest, when controlling for local abundances. Corridors consisted of 1–5 m of riparian vegetation and 90 –110 m of forest. Visual surveys were used in clearcuts and mist nets in corridors. A replicated, controlled study as part of the same study as (1) in mixed boreal forests in northern Alberta, Canada (2), found significantly higher abundances of resident songbirds and woodpeckers, but not of forest specialists, in forest plots connected to a continuous block when compared to isolated fragments. Resident species were found at similar abundances in connected fragments and unfragmented forests, whilst habitat generalists were found at similar abundances across all forest types. None of the individual species analysed appeared to benefit from connectivity. Forest fragments were 10 or 40 ha, either in continuous forest, isolated by a 200 m strip of clearcut on all sides or isolated on three of four sides for connected fragments. Three replicates of each treatment were established in the winter of 1993–4 and monitored until 1998. (1) Machtans, C. S., Villard, M.-A. & Hannon, S. J. (1996) Use of riparian buffer strips as movement corridors by forest birds. Conservation Biology, 10, 1366 –1379. (2) Hannon, S. J. & Schmiegelow, F. K. A. (2002) Corridors may not improve the conservation value of small reserves for most boreal birds. Ecological Applications, 12, 1457–1468.

2.3.

Provide or retain un-harvested buffer strips

• Four replicated studies from Canada and the USA (1,3,5,7) found that wider buffer strips retained a bird community more similar to that of uncut forest than narrower strips. Two replicated and controlled studies from the USA (3,4) found that several forest-specialist species were absent from buffers up to 70 m wide. • Two replicated and controlled studies from the USA (3,7) found that richness was higher in buffers 50% of depredations. The authors suggest leaving wide (>150 m) buffer strips along riparian zones to reduce edge-related nest predation. Artificial nests were placed at five points (100 m apart) along transects that ran parallel to the stream. A replicated, controlled study from May–June in 1994 in 12 riparian buffer-strip (18–70 m wide) sites and four unlogged riparian sites of old-growth forest in Oregon, USA (3) found that 27 species were recorded at unlogged and 42 species at buffer-strip sites: eight species were more abundant in unlogged and 12 species more abundant in buffer-strip sites. Four species that were more abundant in unlogged stands increased with increasing width of riparian buffers. However, four other species were rarely observed in even the widest buffers sampled (40 –70 m). Overall, bird species richness and abundance were not related to bufferstrip width, but the author recommends buffer widths >40 m and maintaining a high density of trees within the buffer. A replicated, controlled paired sites study from June–July in 1994–5 in 16 pairs of forested buffer strips (20 –50 m) and undisturbed riparian coastal forest in Newfoundland, Canada (4), found that bird abundance was higher in the buffer strips (average of 10.5 individuals/transect for buffer strips vs. 7.9 for control sites), total species richness was similar (7.2 species/ transect in buffers vs. 6.2 in controls) but that three of six specialist forest species were absent. Abundance of forest generalist, interior forest, and riparian species were similar between buffers and controls and did not increase in wider buffers. Buffer strips were adjacent to 3 –5 year-old clearcuts (>10 ha) and were typically >300 m long. A replicated controlled before-and-after study in a managed Douglas-fir Pseudotsuga menziesii forest in Washington, USA (5), found that 31 m wide riparian buffer strips contained bird communities that were more similar to control (unharvested) forests than 14 m strips. Forest species (black-throated grey warbler Dendroica nigrescens, golden-crowned kinglet Regulus satrapa and brown creeper Certhia americana) decreased in buffer treatments (especially the narrow buffer) relative to controls. Species of shrubby habitats (dark-eyed junco Junco hyemalis, cedar waxwing Bombycilla cedrorum and song sparrow Melospiza melodia) increased

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in one or both buffer treatments. Birds were surveyed in 18 sites (six of each treatment) in both pre-harvest (spring 1993) and post-harvest (1995 and 1996) years. A replicated controlled trial along a stream in Minnesota, USA (6), found that bird species responded differently to timber harvest in riparian buffers, and that any amount of harvest affected breeding bird communities. Along the stream, 30 m wide forest buffers were established within plots with four treatments (3 plots/treatment): 1) no harvest in buffer; 2) reduction of tree basal area to 7–10 m2/ha; 3) reduction to 2 m2/ha (i.e. clearcut); and 4) no harvest in buffer or adjacent upland forest. Bird surveys were conducted 1 year prior to and for 4 years after, harvest. In the first year after harvest, bird community composition changed in all buffer treatments relative to control plots, and diverged over time. More individuals and species (primarily associated with edge or early-successional habitats) colonised harvested buffers; abundances and species richness of interior forest species declined. A replicated, randomised, controlled study from May–June in 2001 and May–July in 2002 in 24 buffer-strip blocks and 18 continuous, old-growth forest blocks in coastal, temperate forests in Alaska, USA (7) found that species richness was similarly distributed across treatments and controls (both averaged 15 species/100 detections). Species richness and diversity were greatest in the narrowest buffers (1 km apart) in Iowa, USA (18), found that species richness and abundance of grassland birds was similar between strips planted with warm-season grasses, compared to cool-season grasses, but that strips next to woody streamside vegetation held fewer species (6/site) than those with adjacent non-woody vegetation (8 species/site). Nest success was low in all treatments (only 27% of nests fledged at least one nestling) due chiefly to predation (85% of all nests). Cool-season species included brome grass, orchard grass Dactylis glomerata and timothy Phleum pratense; warm-season strips were planted mainly with switchgrass Panicum virgatum. A replicated controlled study in the breeding seasons of 2000 –1 in two restored-mine grasslands and two control (unmined) grasslands (8 –18 ha) in Kentucky, USA (19), found that Henslow’s sparrow territory size was generally smaller on restored grasslands (on 1 May, 0.29 ha/territory for 25 nests on restored sites vs. 0.34 ha/territory for 18 nests on control sites; 15 July: 0.33 ha/territory for 25 nests vs. 0.45 for 17). Average clutch size (3.8) and average number of fledglings per nest (of 48 nests, 28 fledged at least one young) were similar between sites. More insect prey was present on the reclaimed sites. A replicated, controlled study from March–May 2001–2 in two riparian oak forest sites in Missouri, USA (20), found that red-winged blackbird territory area and density were similar between four blocks planted with oak seedlings and seeded with redtop grass Agrostis gigantean and those not seeded (1,657 m2/territory and 0.6 territories/ha for two seeded blocks vs. 1,852 and 0.6 for unseeded blocks). This study is discussed in more detail in ‘Restore or create forests’. A study in 1999 –2000 on the reclaimed Chinook mine (39 – 67 ha) and Universal mine sites in south-west Indiana, USA (21), found 465 bird nests of 31 species at Chinook and 446 at Universal. Red-winged blackbird, eastern meadowlark, field sparrow, dickcissel, grasshopper sparrow and Henslow’s sparrow were the commonest nesting birds. Reproductive success (i.e. nests that fledged young) of key species, e.g. Henslow’s sparrow (9 of 21 nests fledged young) and grasshopper sparrow (26 of 41), and of several other species was comparable with that in non-mined grassland habitats. Both sites were seeded with (mostly) non-native grasses and were situated in open grassland; shrub/savanna; and grassland with patches of shrubs. A before-and-after study in southern Iceland in 2009 (22) found that eight species of birds were found in the study site following the revegetating of ‘sandplains’, but no birds were found in barren sandplains or strips of lyme grass Leymus arenarius. Meadow pipits Anthus pratensis, common snipe Gallinago gallinago and redshank Tringa totanus were the most common species and found at highest abundances in dense areas of Nootka lupin Lupinus nootkathensis (210 meadow pipits/km2, 46 snipe/km2 and 19 redshank/km2 vs. 83 pipits/km2 and 13 snipe/km2 in areas of scattered lupins). Only meadow pipits were found in any habitat without lupins. Revegetation began in earnest in 1988, when areas were sown with lyme grass (65 kg seeds/ha), followed by lupin strips from 1992 (4 kg seeds/ha) and non-native grasses. All treatments except lupins were also fertilised. A replicated, randomised, controlled study from May–July in 2004 –2005 in Kansas and Oklahoma, USA (23), found that overall bird diversity and evenness was significantly higher in ten native prairie hayfields (both burned and unburned) and 18 grazed pastures than eight grass-restored fields. Seven species were recorded and three analysed: dickcissel density was highest in restored fields but nest success was highest and nest parasitism lowest in unburned

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hayfields (48% compared to 16% on average in other sites). Conversely, grasshopper sparrow density was highest in grazed pastures but nest success was lowest in these pastures and highest in burned hayfields (57% compared to 12% on average in other sites). Management did not influence density and nest survival of eastern meadowlarks, which were uniformly low across the region. (1) Burger, G. V., and Linduska, J. P. (1967) Habitat management related to bobwhite populations at Remington farms. The Journal of Wildlife Management, 31, 1–12. (2) Blankespoor, G. W. (1980) Prairie restoration: Effects on nongamebirds. The Journal of Wildlife Management, 44, 667– 672. (3) Wray, T., Strait, K. A., and Whitmore, R. C. (1982) Reproductive success of grassland sparrows on a reclaimed surface mine in West Virginia. The Auk, 99, 157–164. (4) Johnson, D. H., and Igl, L. D. (1995) Contributions of the Conservation Reserve Program to populations of breeding birds in North Dakota. The Wilson Bulletin, 107, 709 –718. (5) Granfors, D. A., Church, K. E., and Smith, L. M. (1996) Eastern meadowlarks nesting in rangelands and Conservation Reserve Program fields in Kansas. Journal of Field Ornithology, 67, 222 –235. (6) Millenbah, K. F., Winterstein, S. R., Campa III, H., Furrow, L. T., and Minnis, R. B. (1996) Effects of Conservation Reserve Program field age on avian relative abundance, diversity, and productivity. The Wilson Bulletin, 108, 760 –770. (7) Delisle, J. M., and Savidge, J. A. (1997) Avian use and vegetation characteristics of Conservation Reserve Program fields. The Journal of Wildlife Management, 61, 318 – 325. (8) Herkert, J. R. (1997) Population trends of the Henslow’s sparrow in relation to the Conservation Reserve Program in Illinois, 1975 –1995. Journal of Field Ornithology, 68, 235 –244. (9) Wakeham-Dawson, A., and Aebischer, N. J. (1998) Factors determining winter densities of birds on environmentally sensitive area arable reversion grassland in southern England, with special reference to skylarks (Alauda arvensis). Agriculture, Ecosystems & Environment, 70, 189 –201. (10) Wakeham-Dawson, A., Szoszkiewicz, K., Stern, K., and Aebischer, N. J. (1998) Breeding skylarks Alauda arvensis on Environmentally Sensitive Area arable reversion grass in southern England: survey-based and experimental determination of density. Journal of Applied Ecology, 35, 635 – 648. (11) McCoy, T. D., Ryan, M. R., Kurzejeski, E. W., and Burger, L. W. (1999) Conservation reserve program: source or sink habitat for grassland birds in Missouri? The Journal of Wildlife Management, 63, 530 – 538. (12) Bajema, R. A., DeVault, T. L., Scott, P. E., and Lima, S. L. (2001) Reclaimed coal mine grasslands and their significance for Henslow’s sparrows in the American midwest. The Auk, 118, 422 – 431. (13) McMaster, D. G., and Davis, S. K. (2001) An evaluation of Canada’s Permanent Cover Program: Habitat for grassland birds? Journal of Field Ornithology, 72, 195 –210. (14) Reynolds, R. E., Shaffer, T. L., Renner, R. W., Newton, W. E., and Batt, B. D. J. (2001) Impact of the Conservation Reserve Program on duck recruitment in the U.S. Prairie Pothole region. The Journal of Wildlife Management, 65, 765 –780. (15) DeVault, T. L., Scott, P. E., Bajema, R. A., and Lima, S. L. (2002) Breeding bird communities of reclaimed coal-mine grasslands in the American midwest. Journal of Field Ornithology, 73, 268 –275. (16) Fletcher, R. J., and Koford, R. R. (2002) Habitat and landscape associations of breeding birds in native and restored grasslands. The Journal of Wildlife Management, 66, 1011–1022. (17) Scott, P. E., and Lima, S. L. (2004) Exotic grasslands on reclaimed midwestern coal mines: An ornithological perspective. Weed Technology, 18, 1518 –1521. (18) Henningsen, J. C., and Best, L. B. (2005) Grassland bird use of riparian filter strips in southeast Iowa. The Journal of Wildlife Management, 69, 198 –210. (19) Monroe, M. S., and Ritchison, G. (2005) Breeding biology of Henslow’s sparrows on reclaimed coal mine grasslands in Kentucky. Journal of Field Ornithology, 76, 143 –149. (20) Furey, M. A., and Burhans, D. E. (2006) Territory selection by upland red-winged blackbirds in experimental restoration plots. The Wilson Journal of Ornithology, 118, 391– 398. (21) Galligan, E. W., Devault, T. L., and Lima, S. L. (2006) Nesting success of grassland and savanna birds on reclaimed surface coal mines of the midwestern United States. The Wilson Journal of Ornithology, 118, 537– 546. (22) Gunnarsson, T. G., and Indridadottir, G. H. (2009) Effects of sandplain revegetation on avian abundance and diversity at Skogasandur and Myrdalssandur, South Iceland. Conservation Evidence, 6, 98 –104. (23) Rahmig, C. J., Jensen, W. E., and With, K. A. (2009) Grassland bird responses to land management in the largest remaining tallgrass prairie. Conservation Biology, 23, 420 – 432.

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Restore or create traditional water meadows

11.3.

235

Restore or create traditional water meadows

• Four out of five before-and-after studies, all from the UK (2 – 5), found that the number of waders and wildfowl on sites increased following the restoration of water meadows. One before-andafter study from Sweden (1) found no increase in northern lapwing population following an increase in the area of managed meadows in the study area. This study also found that restored meadows were used less than expected by breeding lapwings. • A before-and-after study from Sweden (1) found that hatching success of northern lapwings were higher on meadows than on spring-sown crops. There were no differences between meadows and autumn-sown crops or grasslands.

Background Water meadows are areas of grazing land or hay meadow that have carefully controlled water levels to keep the soil damp. In Europe they provide valuable breeding habitats for waders and other biodiversity. The studies below describe instances when multiple interventions have been used to create water meadows. When the effects of multiple interventions, such as raising water levels and adding foot drains, can be separated, they are discussed under the relevant interventions in ‘Threat: Natural system modifications’. A before-and-after study in 1984 –1994 in Västmanland, Sweden (1), found that there was no increase in northern lapwing Vanellus vanellus population in the study area despite an increase in the area of managed flood meadows from 163 ha to 530 ha over the study period (approximately 220 pairs in 1985 vs. 200 in 1994; range of 152 –297 pairs). Both managed and unmanaged meadows were used less for nesting than expected based on their availability. However, average hatching success was significantly higher in meadows (78 –90% for 54 nests in meadows), compared to spring-sown crops (29 – 50% of 1,236 nests). There were no differences between meadows and autumn sown crops or cultivated grassland (approximately 85% and 75% success respectively). Before 1984, the majority of meadows in the area were overgrown and abandoned. A before-and-after study of grazing marshes in east England (2) found an increase in breeding wader numbers following a number of interventions. Northern lapwing numbers increased from 19 pairs in 1993 to 85 pairs in 2003 and common redshank Tringa totanus rose from four to 63 pairs. Numbers of winter wildfowl also increased over the period and changes in vegetation communities to those more tolerant of inundation occurred. In 1993, water levels were raised by 45 cm. Management included opening up existing footdrains; creating new ones; reconnecting drains to ditches; reducing grazing intensity (from 1.5 – 2 cattle/ha to 0.7) and stopping fertiliser inputs. From 1995, approximately 600 m of footdrains were opened/year; from 2000 onwards, approximately 2,000 m of footdrains were opened or added. A study on 84 ha of former arable land adjoining Berney Marshes RSPB Reserve, Norfolk, England (3), found that breeding wader numbers increased after the land was restored to grazing marsh: 15 –20 pairs of northern lapwing and 5 –10 pairs of common redshank were found on the marsh, depending on year. The fields were regularly used for foraging by a large proportion of the estimated 100,000 wintering waterfowl (e.g. Eurasian wigeon Anas penelope) using the reserve. The fields were acquired in 1998, water levels were raised, foot drains were added, and grazing by sheep (and then cattle) was introduced. By 2003, plant communities had shifted towards those characteristic of lowland wet grassland. A before-and-after study on a wetland reserve in Cumbria, England (4), found that the number of common snipe Gallinago gallinago nesting in an area of improved peat grassland increased from one pair in 2003 to 11 pairs in both 2004 and 2005 following several interventions including maintaining higher water levels, the initiation of a more intensive grazing regime, the cutting of rush Juncus spp. the creation of scrapes for feeding birds.

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A before-and-after study on 160 ha of improved grassland at Ynys-hir RSPB reserve, Powys, Wales (5), found that, after a series of management interventions, the population of northern lapwings increased from 10 to 81 pairs and redshank increased from 11 to 29 pairs between 2000 and 2005. Management included chisel ploughing, used on a 2-year rotation (approximately 8 ha in February 2002 and 10 ha areas thereafter) to break up the surface to create small hummocks and divots (see ‘Create scrapes and pools in wetlands and wet grasslands’). The water level was also increased and a seasonal sheep and cattle grazing regime introduced. (1) Berg, A., Jonsson, M., Lindberg, T., and Källebrink, K. G. (2002) Population dynamics and reproduction of northern lapwings Vanellus vanellus in a meadow restoration area in central Sweden. Ibis, 144, E131–E140. (2) Smart, M., and Coutts, K. (2004) Footdrain management to enhance habitat for breeding waders on lowland wet grassland at Buckenham and Cantley Marshes, Mid-Yare RSPB Reserve, Norfolk, England. Conservation Evidence, 1, 16 –19. (3) Lyons, G., and Ausden, M. (2005) Raising water levels to revert arable land to grazing marsh at Berney Marshes RSPB Reserve, Norfolk, England. Conservation Evidence, 2, 47– 49. (4) Holton, N., and Allcorn, R. I. (2006) The effectiveness of opening up rush patches on encouraging breeding common snipe Galliango gallinago at Rogersceugh Farm, Campfield Marsh RSPB reserve, Cumbria, England. Conservation Evidence, 3, 79 – 80. (5) Squires, R., and Allcorn, R. I. (2006) The effect of chisel ploughing to create nesting habitat for breeding lapwings Vanellus vanellus at Ynys-Hir RSPB reserve, Powys, Wales. Conservation Evidence, 3, 77–78.

11.4.

Restore or create shrubland

• Only one of the four studies captured investigated the effects of shrubland restoration in isolation. This small before-and-after study from the UK (2) found that one or two pairs of northern lapwing bred on an area of restored moorland, whereas none had previously bred in the area. • A study from the USA (1) and one from the Azores (3) found that populations of target species (gamebirds and seabirds) increased following shrubland restoration, amongst other interventions. • A replicated study from the UK (4) which did not distinguish between several interventions performed found a negative relationship between the combined intervention and the ratio of young-to-old grey partridges.

Background Shrublands are extremely diverse habitats, being found from subantarctic regions, through temperate climates to tropical dry and moist shrublands such as karoo (in South Africa) and restingas (in Brazil). They are also found from sea level up to beyond the tree line in mountains. However, we found relatively few studies describing the effects of shrubland restoration on bird populations, so we have not subdivided the studies further. A small 1967 study in Maryland, USA (1), investigated the impact of planting areas of shrub, as well as other interventions, on northern bobwhites Colinus virginianus and found that the population on the farm increased from five to 38 coveys in eight years. This study is described in detail in ‘Threat: Agriculture – Plant new hedges’. A small before-and-after study on an area of purple moor grass Molina caerulea dominated moorland in northern England (2) in 2004 – 5 found that one or two pairs of northern lapwing Vanellus vanellus bred on an area of restored moorland, whereas none had previously bred in the area. The moorland was mowed and flailed in 2004, which encouraged grass re-growth and subsequent heavy grazing by both livestock and wild red deer Cervus elaphus. A before-and-after study on Praia Islet (12 ha), off Graciosa, Azores, Portugal (3), found that the breeding populations of common terns Sterna hiundo, roseate terns S. dougallii and

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Madeiran storm petrel Oceanodroma castro increased dramatically after European rabbit Oryctolagus cuniculus eradication and subsequent habitat restoration. Restoration included the planting of native shrubs, the removal of non-native species and the control of soil erosion. This study is also discussed in ‘Provide artificial nesting sites’ for ground-nesting and burrow-nesting seabirds. A replicated site comparison study on 1,031 agricultural sites across England in 2004 – 8 (4) investigated the impact of scrub restoration on grey partridge Perdix perdix. However, the study does not distinguish between the impacts of scrub restoration, scrub control, rough grazing and the restoration of various other semi-natural habitats. There was a negative relationship between the combined intervention and the ratio of young to old partridges in 2008. (1) Burger, G. V., and Linduska, J. P. (1967) Habitat management related to bobwhite populations at Remington farms. The Journal of Wildlife Management, 31, 1–12. (2) Smith, D., and Bird, J. (2005) Restoration of degraded Molinia caerulea dominated moorland in the Peak District National Park Eastern moorlands, Derbyshire, England. Conservation Evidence, 2, 101–102. (3) Bried, J., Magalhaes, M. C., Bolton, M., Neves, V. C., Bell, E., Pereira, J. C., Aguiar, L., Monteiro, L. R., and Santos, R. S. (2009) Seabird habitat restoration on Praia Islet, Azores Archipelago. Ecological Restoration, 27, 27– 36. (4) Ewald, J. A., Aebischer, N. J., Richardson, S. M., Grice, P. V., and Cooke, A. I. (2010) The effect of agri-environment schemes on grey partridges at the farm level in England. Agriculture, Ecosystems & Environment, 138, 55 – 63.

11.5.

Restore or create savannas

• We captured no evidence for the effects of savanna restoration or creation on bird populations.

11.6.

Restore or create wetlands and marine habitats

11.6.1.

Restore or create inland wetlands

• Of eleven studies captured, 11, from the mainland USA (1,2,5,6), Guam (3), Canada (8) and Hawaii (10), found that birds used artificially restored or created wetlands. Two found that rates of use and species richness were similar or higher than on natural wetlands (6,10). One found that use rates were higher than on unrestored wetlands (8). • Three studies from the USA (5,7) and Puerto Rico (9) found that restored wetlands held lower densities and fewer species of birds than natural wetlands. • A replicated study from the USA (5) found that least bittern productivity was similar in restored and natural wetlands. • Two replicated studies examined wetland characteristics: one from the USA (11) found that semi-permanent restored wetlands were used more than temporary or seasonal ones. A study from Hawaii (10) found that larger restored wetlands were used more than smaller sites.

Background This section includes studies describing the effects of wetland restoration or creation for all wetlands which are not coastal, or do not receive regular influxes of salt water. A study in 1958 –1967 on Squaw Creek National Wildlife Refuge, Missouri, USA (1), found that annual use of the 2,772 ha wetlands (created in 1935) varied from 6 –27 million duck-days and from 7–19 million goose-days each year. Management included winter water removal to aerate the soil and eradicate carp, and spring flooding. A study in 1986 at the Savannah River Site, South Carolina, USA (2), found that up to 94 wood storks Mycteria americana and over 210 other wading birds were seen on specially

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constructed and managed ponds at once. Ponds were created in a 14 ha depression and stocked with fish between 1985 and 1986. A before-and-after study in 1992 on Guam, South Pacific (3), found that Mariana common moorhens Gallinula chloropus guami colonised a newly-created wetland within five months of its creation, with two adults and at least four chicks being seen. The wetland was 20 – 60 cm deep, 45 m long and up to 27 m wide and created using an excavator in January 1992. Spikerush Eleocharis dulcis, water lettuce Pistia stratiotesm, taro Colocasia esculenta and rusty flatsedge Cyperus odoratus were planted, although the taro died, probably because of excessive flooding. A replicated, controlled study in 1992 –1994 in wetlands in the Lake Ontario and St. Lawrence River plains, New York State, USA (4), found lower species richness and densities of wetland birds on restored wetlands compared with natural wetlands (6 species/ha and 15 birds/ha for 18 restored sites vs. 8 and 20 for eight natural sites). This pattern was stronger for wetland dependent species. Restored sites also had community compositions more similar to other restored sites than to natural wetlands. Birds were surveyed with an unlimited-radius point count within each wetland each year during the breeding season. A replicated study from April–June in 1985 –1991 in a 13 ha wetland site in South Carolina, USA (5), found that least bitterns Ixobrychus exilis nested at high densities (12 pairs/ha), had a 50% hatching rate and 55% of nests produced fledglings. The author points out that this rate is only slightly lower than that reported for natural wetlands. An average of 2.7 fledglings/ nest were produced from an average 3.8 eggs/clutch. Most egg mortality was caused by nest instability. A replicated, paired site study from May–July in 1997–1998 in 39 pairs of restored and natural wetlands in North and South Dakota, USA (6) found that restored wetlands exhibited equal, and often greater, avian abundance, species richness and diversity. There were no significant differences in overall bird abundance, species richness or diversity; waterfowl breeding pair density or upland species richness between restored and natural wetlands. However, Canada goose Branta canadensis, mallard Anas platyrhynchos, redhead Aythya americana, and ruddy duck Oxyura jamaicensis exhibited significantly higher densities on restored wetlands. Total area bird counts were performed four times on each wetland. A replicated, controlled study from May–July in 2000 in Virginia, USA (7), found that bird species richness and diversity in artificially created wetlands were significantly lower than in natural wetlands (average of 11 species/site for six artificial wetlands vs. 17 for five natural wetlands). Although total bird abundance, and the abundance of wading birds, waterfowl, raptors, aerial feeders or woodpeckers were similar, natural wetlands had significantly higher songbird abundance. In addition, created wetlands exhibited bird communities with significantly lower conservation value (based trophic level and migratory status) but similar average habitat specificity and wetland dependency. All wetlands had similar surrounding habitats and were of similar ages (time since planting for created and since logging for natural wetlands), and sizes (5 –15 ha). A replicated, controlled study in April 1998 –1999 on Prince Edward Island, Canada (8), found that six out of eight wildfowl species were found in significantly higher numbers in 22 restored wetlands than in 24 control (unrestored) wetlands. Four species also had significantly more broods at restored sites. Large wetlands, close to rivers and with a large proportion of cattails Typha spp. held more species than other sites. All sites were freshwater wetlands, 0.3 – 6.0 ha in size and restored sites were dredged, starting in 1990, to remove excess organic material. A small controlled study from 2004 –2005 in Toa Baja, Puerto Rico (9) found that fewer bird species were recorded in an 18 ha restored forested wetland than in a natural forested wetland (nine records of five species in restored site vs. 65 records of 16 species in the natural site). In addition, only one species (yellow-faced grassquit Tiaris olivaceus) was observed foraging in the restored wetland; 40% of records in the natural site were of foraging birds. Only two records, both of northern waterthrush Seiurus novaboracensis were made at a 14 ha

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control (unrestored) grassland site. The restored wetland was planted with 7,000 Pterocarpus officinalis and Annona glabra trees during 1997–2000. A replicated, randomised study in spring from 2004 – 5 in 28 small restored wetlands in Illinois, USA (10), found that semi-permanent wetlands were used more frequently by waterbirds than temporary or seasonal wetlands and held more waterfowl broods (semipermanent wetlands were used on 56% of days and held 1.1 broods/ha vs. 37% and 0.2 for seasonal and 7% and zero broods for temporary wetlands). Hydrologic management (passive restoration and management; active restoration through hydraulic engineering but passively managed or actively restored and managed through regulation of hydrologic regime) was the most important variable in explaining bird abundance and distributions. Of the 28 wetlands, 25 were 60 small islands in Archipelago National Park, south-west Finland (1) found that, following the removal of up to 63 introduced and predatory American mink Mustela vison each year in 1992 – 3 and 1998, experimental areas had significantly higher species richness and abundance, compared to control areas. There was a significant positive relationship between the degree of isolation of the islands and species richness and abundance in control, but not experimental areas. In all areas, larger islands had more pairs and more species. A 2010 literature review (2) found that all five successful invasive mammal eradication and control programmes on United Kingdom Overseas Territories found native bird population recoveries and/or recolonisations following the programmes. Recovering species included seabirds and songbirds. The impacts of ten more eradication programmes have not been recorded or published, whilst a final eradication attempt (in the British Indian Ocean Territories) failed to remove black rats Rattus rattus. Eradicated/controlled species included pigs Sus scrofa, cats Felis catus, rats Rattus spp., dogs Canis familiaris and grey fox Dusicyon griseus. (1) Nordstrom, M. & Korpimaki, E. (2004) Effects of island isolation and feral mink removal on bird communities on small islands in the Baltic Sea. Journal of Animal Ecology, 73, 424 – 433. (2) Hilton, G. M. & Cuthbert, R. J. (2010) The catastrophic impact of invasive mammalian predators on birds of the UK Overseas Territories: a review and synthesis. Ibis, 152, 443 – 458.

12.3.1.

Wildfowl

• A before-and-after study from Alaska (1) found that cackling geese Branta hutchinsii returned to a total of eight nesting islands between the 1970s and 1991, following the removal of Arctic foxes Alopex lagopus from the islands. A before-and-after study from the Aleutian Islands, Alaska, USA on the cackling goose Branta hutchinsii recovery programme (1) found that geese bred on four islands from 1984 onwards after Arctic foxes Alopex lagopus were eradicated from them. Together with releases of captive-bred individuals, the programme resulted in the population increasing to 6,000

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birds by 1991, compared with fewer than 1,000 in the 1970s, and birds were breeding on eight fox-free islands. The effects of different release techniques are discussed in ‘Release captivebred individuals into the wild to restore or augment wild populations’, ‘Release birds as adults or subadults, not juveniles’ and ‘Clip birds’ wings on release’. (1) USFWS (2001) Aleutian Canada goose road to recovery. U.S. Fish & Wildlife Service report.

12.3.2.

Seabirds

• We found 16 before-and-after studies, one paired sites study and one literature review from around the world, all describing positive seabird responses to the removal or control of mammalian predators (mainly rats Rattus spp. and feral cats Felis catus) from islands. • Of these 18 studies, seven (4,5,9,12,16 –18) found either large population increases or recolonisations following predator eradication or control. Two of these found only partial population increases or recolonisations: a study from Alaska (4,16). • Twelve studies found increases in reproductive success and survival (1– 3,5,7,8,11,13,15) or decreases in predation and mortality (1,2,5,6,8,10,13,14) following predator control. In one case (13) there was also a small population increase. • Rats and mice Mus musculus were controlled in twelve studies (2,3,5,7–12,15 –17), mostly examining burrow-nesting seabirds; cats in eight (1,2,5,6,10,13,14,18), mostly on ground or cliffnesting seabirds; and other species in two (2,4).

Background Seabirds frequently nest on the ground, where they are vulnerable to predation by cats Felis catus or pigs Sus scrofa, or in burrows where rats Rattus spp. or even house mice Mus musculus can predate chicks, eggs and adults. In addition, seabirds are often poor walkers (as they are specialised for flying and swimming) and cannot evade predators. Because of this, breeding sites are often confined to offshore islands and their populations can be devastated if predators are introduced. A before-and-after study on the sub-Antarctic Marion Island (290 km2), South Africa (1), found that breeding success of great-winged petrels Pterodroma macroptera, increased from 0 –21% to 56 – 60% following 14 years of cat Felis catus control. In addition, no signs of cat predation were found in 1990, but at least 28% of chicks were predated in 1983. Nests were monitored in 1979 – 80, 1982 and 1984 (between 17 and 53 nests studied) and in 1990 (50 nests). Control consisted of the release of the disease panleucopaenia, shooting and trapping. Two before-and-after studies on two Galápagos Islands, Ecuador (2), found that darkrumped petrel Pterodroma phaeopygia fledging success increased (on Floreana Island, 173 km2) and predation of adults decreased (on Santiago Island, 585 km2) following black rat Rattus rattus and feral animal control. On Floreana, fledging success increased (and nestling predation decreased) from 31% in 1981–2 to 46% (1983) and 72% (1984) with control in 1983 – 4. It declined in 1985 (to 23%) with increased feral cat Felis catus predation of young but increased again following cat control to 70 – 80% in 1986 – 8. Between 83 and 104 nests were studied each year. On Santiago, 55% of 510 monitored adult petrels were predated in 1985, but only six were in 1986, following an 80% reduction in the feral pig Sus scrofa population. Rats were intensively controlled by poisoning with coumatetralyl, whilst pigs, cats, goats Capra hircus and donkeys Equus asnus were shot. This study is also discussed in ‘Provide artificial nesting sites’ and ‘Use vocalisations to attract birds to safe areas’. A replicated and controlled paired sites study in 1993 – 4 in six areas of shrubland on Sand Island, Midway Atoll, Hawaii, USA (3), found that Bonin petrel Pterodroma hypoleuca reproductive success was higher in two out of three areas with black rat Rattus rattus removal (treatment sites), compared to paired control sites (65 –92% success for 144 nests in treatment

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Threat: Invasive alien and other problematic species

sites vs. 0 –96% for 144 in controls). In addition, the number of nests that failed because of rat predation was significantly lower in treatment sites (overall, 41% of 17 failed nests in treatment areas were due to rats vs. 95% of 41 nests in control areas, 48 nests monitored at each site). Rats were controlled with the rodenticide Bromothalin dispensed from bait stations. The authors note that early in the 1993 breeding season, there was limited poisoning in the control sites as well, which may have resulted in higher than expected breeding success in these sites. A controlled before-and-after study on Simeonof (4,000 ha) and Chernabura (3,000 ha) Islands in the Shumagin Islands, Alaska (4) found that the average number of pigeon guillemots Cepphus columba recorded increased from 28 to 46 individuals on Chernabura, between 1994 and 1995, following the eradication of introduced arctic foxes Alopex lagopus. There was no increase on Simeonof Island, with an average of four recorded in both years. Guillemot densities were significantly lower than on islands without foxes. A before-and-after study on Madeira (741 km2), Portugal between 1985 and 2000 (5) found that the population of Zino’s petrel Pterodroma madeira on the five known breeding ledges increased from 12 pairs in 1987 to 29 pairs in 2000, following black rats Rattus rattus and cats Felis catus control. In 1987 (prior to cat control), ten adult petrels were killed by cats but only four were found dead between 1992 and 2000, of which two had been partially eaten by cats. Rats were controlled using 65 brodifacoum bait boxes, first set in 1986; cats were caught in traps, with eight placed in 1991, increasing to 17 by 2000. A replicated before-and-after study on Natividad Island (7.4 ha), Baja California Sur, Mexico (6), found that mortality rates of black-vented shearwaters Puffinus opisthomelas in four survey plots fell by 90%, from 7.4 carcasses/month (April–July 1997) to 0.7 carcasses/ month (March–June 2002) following the eradication of feral cats Felis catus from the island. Extrapolated to the entire colony, this suggests a decrease in mortality from over 1,000 birds/ month to fewer than 90 birds/month, with each of 25 cats killing approximately 37 birds/ month. A before-and-after study on The Chicken Islands, North Island, New Zealand (7) found that nesting success of Pycroft’s petrel Pterodroma pycrofti and little shearwater Puffinus assimilis increased from 20% in 1992 – 3 to 75% in 1994 – 5, following the eradication of Pacific rat Rattus exulans from Lady Alice Island (1.4 km2) in 1994. Rats were eradicated using brodifacoum-impregnated cattle feed. A before-and-after study on Congreso (25.6 ha), Chafarinas Islands, Spain, between 1997 and 2004 (8) found breeding success of Cory’s shearwaters Calonectris diomedea at two subcolonies increased when black rats Rattus rattus were intensively controlled and fell when control was relaxed. Success was 27– 44% and 51% during two periods of little or no control (1997– 8, 2000), compared with 70% and 71% during intensive control (2000 and 2002 – 4). Increases were due to decreased chick mortality from 52% and 23% in 1999 and 2001 to 11% in 2000. The increase in breeding success after control was greater at the more easily accessible colony, although that colony had lower breeding success overall. Between 208 and 280 nests were studied each year. A before-and-after study on Lundy Island (445 ha), south-west UK (9) found that Manx shearwaters Puffinus puffinus and Atlantic puffins Fratercula arctica both returned to breed on the island after an absence of 45 and 20 years respectively, following the successful eradication (by poisoning) of brown rats Rattus norvegicus and black rats Rattus rattus in 2004. A before-and-after study on Isla Isabelle (194 ha), western Mexico (10) found that mortality rates of adult sooty terns Onychoprion fuscata fell from an estimated 23 – 33% of the nesting population over the breeding season in 1991– 4 to 5% in 1996 and then to 2% in 2002 – 4, following the eradication of cats Felis catus through trapping, poisoning (with 1080 sodium monofluoroacetate) and shooting. An attempted eradication of black rats Rattus rattus at the same time, using brodifacoum poisoning failed. A before-and-after study on Mokoli’i Island (1.6 ha), Hawaii, USA (11), found that the reproductive output of wedge-tailed shearwaters Puffinus pacificus increased from a single chick between 1999 and 2001 to 126 chicks in 2002 and 185 in 2003, following the eradication

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of black rats Rattus rattus between March and October 2002. Rats were eradicated using diphacinone bait and snap and cage traps. A controlled before-and-after study on Langara Island (3,270 ha), British Columbia, Canada (12), found that the estimated population of ancient murrelets Synthliboramphus antiquus increased from 13,000 (1999) to 24,000 (2004), following the eradication of brown rats Rattus norvegicus in 1995 through brodifacoum poisoning. This followed a period of population decline between 1981 and 1999. On islands without eradication programmes (and on Langara Island between 1981–99), ancient murrelet populations declined if rats were present (22% over ten years on Lyell Island, 50% over seven years followed by extirpation on Kunghit Island) and were stable or increasing on islands without rats. A population of Cassin’s auklets Ptychoramphus aleuticus (previously extirpated on Langara) also re-established following rat eradication. A before-and-after study over 17 years (1990 –2007) on Ascension Island (88 km2), South Atlantic (13), found that the sooty tern Onychoprion fuscata population increased (though not significantly) from 302,000 – 417,000 birds (1990 and 2001) to 420,000 (2007), following feral cat Felis catus eradication in 2002 – 4. The authors note that no increase would be expected until 2008 due to the breeding cycle of the terns. Predation by cats fell from 33 birds/night (early 1990s) to zero birds/night (2003), and overall nesting success rose from 54% of 233 nests to 68% of 656 nests. Following cat eradication, there was a significant increase in the number of tern chicks being predated by rats, from zero prior to cat eradication (473 days of monitoring) to 46% of 200 chicks ringed in 2005 (40 days of monitoring). Cats were removed through poisoning (with 1080 sodium monofluoroacetate), trapping and other methods (started in 2002, completed 2004). A before-and-after study on Juan de Nova Island (4.4 km2), Mozambique Channel in July–August 2006 (14) found that predation rates on sooty terns Sterna fuscata fell from an estimated 2,205 terns/week to 416 terns/week following the control of feral cats Felis catus. Forty three cats were removed through trapping and shooting, leaving an estimated ten remaining. Predation rates were based on the recovery of 122 tern carcasses, of which 89 (73%) showed signs of predation and consumption and 27 (22%) showed signs of predation but not consumption (‘surplus killing’). A before-and-after study on Selvagem Grande (245 ha), Madeira Archipelago, Portugal (15), found that breeding success and productivity of Cory’s shearwaters Calonectris diomedia borealis was significantly higher, following the eradication of rabbits Oryctolagus cuniculus and house mice Mus musculus from the island. This paper is discussed in detail in ‘Control or remove habitat-altering mammals’. A review of rat Rattus spp. eradication programmes on five islands around the UK between 1959 and 2006 (16) found that bird populations increased on four of the islands: Atlantic puffins Fratercula arctica have recolonised Ailsa Craig, south-west Scotland and their range and population increased on Handa, north Scotland. Manx shearwaters Puffinus puffinus increased from 700 to 2,000 pairs on Ramsey, west Wales and 308 to 1,120 pairs on Lundy, south-west England (see (9)). However, they did not recolonise Cardigan Island, south-west Wales. A before-and-after study on Feno Islet (1.6 ha), Azores, Portugal between 1997 and 2009 (17) found that both roseate tern Sterna dougallii and common tern S. hirundo populations returned to the islet following the eradication of black rats Rattus rattus in March–April 2007. Pre-rat populations of roseate and common terns were estimated at 340 and 280 pairs respectively, but none bred in 2005. Common terns returned in 2007 and increased to approximately 120 pairs by 2009. Few roseate terns returned in 2007– 8, but 260 pairs bred in 2009. A total of nine rats were trapped on the island. A before-and-after study on Ascension Island (88 km2), South Atlantic (18) found that five species of ground-nesting seabird recolonised the island in small but increasing numbers, following the eradication of cats Felis catus in 2004: white-tailed tropicbird Phaethon lepturus (25 pairs in 2007), red-billed tropicbird Phaethon aethereus eight pairs), brown noddy Anous stolidus (79 pairs), masked booby Sula dactylatra (152 pairs) and brown booby Sula leucogastor

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(29 pairs). All recolonising populations were small (less than 18% of the population breeding in cat-inaccessible sites in 2002) and breeding success for boobies and brown noddy was lower than other populations. The study also found that sooty tern Onychoprion fuscata numbers increased (see reference (13)). Cats were poisoned with 1080 sodium monofluoroacetate and trapped (488 cats poisoned, 70 captured in live traps, nine caught in various methods). (1) Cooper, J. & Fourie, A. (1991) Improved breeding success of great-winged petrels Pterodroma macroptera following control of feral cats Felis catus at subantarctic Marion Island. Bird Conservation International, 1, 171–175. (2) Cruz, J. & Cruz, F. (1996) Conservation of the dark-rumped petrel Pterodroma phaeopygia of the Galapagos Islands, 1982 –1991. Bird Conservation International, 6, 23 – 32. (3) Seto, N. W. & Conant, S. (1996) The effects of rat (Rattus rattus) predation on the reproductive success of the Bonin petrel (Pterodroma hypoleuca) on Midway Atoll. Colonial Waterbirds, 19, 171–185. (4) Byrd, G. V., Bailey, E. P. & Stahl, W. (1997) Restoration of island populations of black oystercatchers and pigeon guillemots by removing introduced foxes. Colonial Waterbirds, 253 –260. (5) Zino, F., Oliveira, P., King, S., Buckle, A., Biscoito, M., Neves, H. C. & Vasconcelos, A. (2001) Conservation of Zino’s petrel Pterodroma madeira in the archipelago of Madeira. Oryx, 35, 128 –136. (6) Keitt, B. S. & Tershy, B. R. (2003) Cat eradication significantly decreases shearwater mortality. Animal Conservation, 6, 307– 308. (7) Parrish, R. (2005) Pacific rat Rattus exulans eradication by poison-baiting from the Chickens Islands, New Zealand. Conservation Evidence, 2, 74 –75. (8) Igual, J. M., Forero, M. G., Gomez, T., Orueta, J. F. & Oro, D. (2006) Rat control and breeding performance in Cory’s shearwater (Calonectris diomedea): effects of poisoning effort and habitat features. Animal Conservation, 9, 59 – 65. (9) Lock, J. (2006) Eradication of brown rats Rattus norvegicus and black rats Rattus rattus to restore breeding seabird populations on Lundy Island, Devon, England. Conservation Evidence, 3, 111–113. (10) Rodríguez, C., Torres, R. & Drummond, H. (2006) Eradicating introduced mammals from a forested tropical island. Biological Conservation, 130, 98 –105. (11) Smith, D. G., Shiinoki, E. K. & VanderWerf, E. A. (2006) Recovery of native species following rat eradication on Mokoli’i Island, O’ahu, Hawai’i. Pacific Science, 60, 299 – 303. (12) Regher, H. M., Rodway, M. S., Lemon, M. J. F. & Hipfner, J. M. (2007) Recovery of the Ancient Murrelet Synthliboramphus antiquus colony on Langara Island, British Columbia, following eradication of invasive rats. Marine Ornithology, 35, 137–144. (13) Hughes, B. J., Martin, G. R. & Reynolds, S. J. (2008) Cats and seabirds: effects of feral domestic cat Felis silvestris catus eradication on the population of sooty terns Onychoprion fuscata on Ascension Island, South Atlantic. Ibis, 150, 122 –131. (14) Peck, D. R., Faulquier, L., Pinet, P., Jaquemet, S. & Le Corre, M. (2008) Feral cat diet and impact on sooty terns at Juan de Nova Island, Mozambique Channel. Animal Conservation, 11, 65 –74. (15) Zino, F., Hounsome, M. V., Buckle, A. P. & Biscoito, M. (2008) Was the removal of rabbits and house mice from Selvagem Grande beneficial to the breeding of Cory’s shearwaters Calonectris diomedea borealis? Oryx, 42, 151–154. (16) Ratcliffe, N., Mitch, I., Varnham, K., Verboven, N. & Higson, P. (2009) How to prioritize rat management for the benefit of petrels: a case study of the UK, Channel Islands and Isle of Man. Ibis, 151, 699 –708. (17) Amaral, J., Almeida, S., Sequeira, M. & Neves, V. (2010) Black rat Rattus rattus eradication by trapping allows recovery of breeding roseate tern Sterna dougallii and common tern S. hirundo populations on Feno Islet, the Azores, Portugal. Conservation Evidence, 7, 16 –20. (18) Ratcliffe, N., Bell, M., Pelembe, T., Boyle, D., Benjamin, R., White, R., Godley, B., Stevenson, J. & Sanders, S. (2010) The eradication of feral cats from Ascension Island and its subsequent recolonization by seabirds. Oryx, 44, 20 –29.

12.3.3.

Gamebirds

• A single replicated and controlled study on two Swedish islands (1) found that four species of gamebirds had larger broods, and more females had chicks, when predators were controlled. Two of the species also showed population-level responses. A replicated, controlled study on two islands (18 km2 and 23.5 km2) in the Gulf of Bothnia, Sweden between 1976 and 1984 (1) found that gamebird brood sizes were significantly larger and a higher proportion of females had chicks over a four year period when predators were controlled, compared to when predators were not removed (with predator control: 5.5 chicks/

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brood, 77% of 378 hens had chicks; without predator control: 3.3 chicks/brood, 59% of 314 hens had chicks). Species studied were capercaillie Tetrao urogallus, black grouse Tetrao tetrix, hazel grouse Bonasa bonasia and willow ptarmigan Lagopus lagopus, with adult capercaillie and black grouse counts increasing by 56 – 80% after predators had been controlled for two years, and counts at leks increasing by 166 –174%. Predators (European pine martens Martes martes and red foxes Vulpes vulpes) were trapped and shot. (1) Marcstrom, V., Kenward, R. E. & Engren, E. (1988) The impact of predation on boreal tetraonids during vole cycles: an experimental study. Journal of Animal Ecology, 57, 859 – 872.

12.3.4.

Rails

• Two before-and-after studies from Australia (1) and the Galapagos Islands (2) found increases in survival or population density of rails on islands following the removal of feral pigs Sus scrofa.

Background Rails have been especially badly affected by introduced predators and other human impacts, with an estimated 800 species becoming extinct in the Pacific alone (Steadman 1995). They have diversified on islands across the world, with many species losing the ability to fly, thus rendering them extremely vulnerable to invasive predators. Steadman, D. W. (1995) Prehistoric extinctions of Pacific island birds: biodiversity meets zooarchaeology. Science, 267, 1123 –1131.

A before-and-after study in 1979 – 84 on Lord Howe Island (56 km2), Australia (1), found that the Lord Howe Island woodhen Tricholimnas sylvestris population increased after feral pigs Sus scrofa were controlled and a captive breeding programme was launched. Before pig control, the woodhen population was a maximum of ten breeding pairs, with adult mortality higher than juvenile recruitment. Following pig control, 56 released, captive-bred birds were found to survive for up to two years and 19 young were successfully raised between 1982 and 1984. Additionally, woodhens have started to expand their range from the unfavourable territories they were previously confined to, to more favourable, previously pig-infested regions. A total of 186 were destroyed between 1979 and 1981. This study is also discussed in ‘Release captive-bred individuals’ and ‘Use captive breeding to increase or maintain populations’. A controlled before-and-after study on Santiago Island (585 km2), Galapagos, Ecuador (2) found that densities of Galapagos rails Laterallus spilonotus increased following the eradication of feral mammals between 1998 and 2006 (279 rails found at 8.5 –17.9 rails/ha in 2004 – 5 vs. 18 rails at 0 –1.4 rails/ha in 1986 –7). Over the same period, there was a smaller increase in rails detected on Ferdandina Island, which has remained free from invasive mammals (no rails detected during surveys in 1986–7 although some were heard outside survey times, 11 rails detected in 2004 –5) and a decrease on Isabella Island, which retains feral goats, pigs and donkeys (13 rails in 247 survey plots at eight sites in 2004 – 5 vs. 24 rails in 60 survey plots in 1986 –7). Donkeys Equus asinus, 17,000 pigs Sus scrofa and 70,000 goats Capra hircus were removed. (1) Miller, B. & Mullette, K. J. (1985) Rehabilitation of an endangered Australian bird – the Lord Howe Island woodhen Tricholimnas sylvestris (Sclater). Biological Conservation, 34, 55 –95. (2) Donlan, C., Campbell, K., Cabrera, W., Lavoie, C., Carrion, V. & Cruz, F. (2007) Recovery of the Galápagos rail (Laterallus spilonotus) following the removal of invasive mammals. Biological Conservation, 138, 520 – 524.

12.3.5.

Waders

• A controlled before-and-after study in New Zealand (2) found that the Chatham Island oystercatcher Haematopus chathamensis population increased following the removal of feral cats Felis catus and other species.

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• A second controlled before-and-after study in Alaska, USA (1), found small increases in black oystercatcher Haematopus bachmani breeding populations on two islands, but the overall population only increased on one, declining on the other. A controlled before-and-after on Simeonof (4,000 ha) and Chernabura (3,000 ha) Islands in the Shumagin Islands, Alaska (1), found that the probable breeding populations of black oystercatchers Haematopus bachmani increased following the eradication of introduced arctic foxes Alopex lagopus (Simeonof: four pairs in 1994 vs. five in 1995; Chernabura: three and five pairs). Total estimated population increased on Simeonof (34 to 41 birds) but decreased on Chernabura (25 to 19 birds). Oystercatcher densities were significantly lower than on islands without foxes. A controlled before-and-after study on Chatham Island (899 km2), New Zealand between 1999 and 2005 (2) found that the number of Chatham Island oystercatchers Haematopus chathamensis breeding in a 14 km stretch of beach increased from 16 to 35 pairs over the study period, following the initiation of control (trapping and shooting) of predators, principally feral cats Felis catus, but also other introduced mammals and weka Gallirallus australis. Birds in the management area fledged 18 – 35 chicks/year, compared with very low fledging success in unmanaged areas. (1) Byrd, G. V., Bailey, E. P. & Stahl, W. (1997) Restoration of island populations of black oystercatchers and pigeon guillemots by removing introduced foxes. Colonial Waterbirds, 20, 253 –260. (2) Moore, P. (2005) Predator control to increase breeding success of Chatham Island oystercatcher Haematopus chathamensis, Chatham Island, New Zealand. Conservation Evidence, 2, 80 – 82.

12.3.6.

Raptors

• A study in Mauritius (1) found that numbers of Mauritius kestrel Falco punctatus may have increased following the trapping of predators near nests. However, the authors do not provide any data to support this observation. A study of an integrated conservation programme for the endangered Mauritius kestrel Falco punctatus from 1973 –1994 in montane forest habitat and a captive breeding centre in Black River, Mauritius (1) found that trapping and removing nest predators may have significantly increased breeding pair productivity. Two introduced predators (small Indian mongoose Herpestes auropunctatus and feral cat Felis catus) were trapped near some wild nests and at all artificial nestboxes. The authors provide no data on the numbers of predators trapped or experimental data on the effects of their removal. (1) Jones, C. G., Heck, W., Lewis, R. E., Mungroo, Y., Slade, G. & Cade, T. (1995) The restoration of the Mauritius kestrel Falco punctatus population. Ibis, 137, S173 –S180.

12.3.7.

Pigeons

• Two before-and-after trials on Mauritius found that fewer pink pigeon Columba mayeri nests were predated (1) and more chicks were fledged (2) following systematic and intensive rat control.

Background The pink pigeon Nesoenas mayeri is an endangered species from Mauritius that declined to just ten wild individuals in 1990 before intensive captive breeding and in situ management. The species is still under pressure from several threats, including predation by introduced mammals: crab-eating macaque Macaca fascicularis, Indian mongoose Herpestes auropunctatus, rats Rattus spp. and feral cats Felis catus (Reese Lind 1994; Swinnerton 2001).

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Reese Lind, C. (1994) Management of the EEP Pink Pigeon Columba (Nesoenas) mayeri population. Dodo: Journal of the Jersey Wildlife Preservation Trust, 30, 106 –113. Swinnerton, K. (2001) Ecology and conservation of the Pink Pigeon Columba mayeri on Mauritius. Journal of the Jersey Wildlife Preservation Trust, 37, 99.

A before-and-after trial in ‘Pigeon Wood’ (mixed forests), Black River Gorges National Park, Mauritius in 1989 –91 (1) found that fewer pink pigeon Nesoenas mayeri (formerly Columba mayeri) nest were predated by rats Rattus spp. in 1992 (12% of eight nests predated), compared to in 1989 –90 (32% of 22 nests predated, following the initiation of systematic rat control (using brodifacoum bait stations). This study is also discussed in ‘Provide supplementary food to increase adult survival’, ‘Use captive breeding to increase or maintain populations’, ‘Release captive bred individuals’ and ‘Provide supplementary food after release’ and ‘Predator control on islands’. A before-and-after trial in Brise Fer, Mauritius (2) found that four pink pigeon Nesoenas mayeri (formerly Columba mayeri) chicks fledged in 2006, during the trialling of a new ‘hockey stick’ bait station to control rats Rattus spp., compared to no successful fledgings in 2005 and ‘few to no chicks’ in the previous few years. (1) Jones, C., Swinnerton, K., Taylor, C. & Mungroo, Y. (1992) The release of captive-bred pink pigeons Columba mayeri in native forest on Mauritius. A progress report July 1987–June 1992. Dodo, 28, 92 –125. (2) Tatayah, R., Haverson, P., Wills, D. & Robin, S. (2007) Trial of a new bait station design to improve the efficiency of rat Rattus control in forest at Black River Gorges National Park, Mauritius. Conservation Evidence, 4, 20 –24.

12.3.8.

Parrots

• Two before-and-after studies in New Zealand (1,2) found reduced nest predation and successful recolonisation of an island following invasive mammal eradication or control.

Background The kakapo Strigops habroptila is a large, flightless parrot, once common across New Zealand but almost wiped out by the late 20th century due to predation of adults by feral cats Felis catus, dogs Canis familiaris and mustelids and the loss of eggs and chicks to rats Rattus spp. Starting in the 1970s, the remaining birds were translocated to islands free from cats and populations were very intensively managed (see ‘General responses to small and declining populations’). The Kermadec red-crowned parakeet Cyanoramphus movazelandiae, also from New Zealand was the first parrot to recolonise an island after predator removal. A small before-and-after study on Codfish Island (1,500 ha), New Zealand (1) found that none of six kakapo Strigops habroptilus nests were lost to rats Rattus spp. in 1997, when there was intensive trapping and poisoning of rats close to nests (in conjunction with remotely operated detonators to scare rats, see ‘Guard nests to prevent predation’). In contrast, there were potentially unsustainable predation rates before 1997. The study does not fully describe the impact of predator control on the species – the translocations and subsequent population stabilisation would only have been possible with prior control. A before-and-after study on Raoul Island (2,938 ha), Kermadec Islands, New Zealand (2) found that the island was recolonised by Kermadec red-crowned parakeets Cyanoramphus movazelandiae in 2008, following the eradication of goats Capra hircus by hunting (in 1986) and cats Felis cattus, brown rats Rattus norvegicus and black rats R. rattus by poisoning and hunting (between 2002 and 2004). In 2008 the parakeet population was at least 100 individuals, of which 44 were born in 2008. Before this, parakeets had been absent for 172 years. (1) Jansen, W. (2005) Rat Rattus control at nests of the endangered kakapo Strigops habroptilus on Codfish Island, New Zealand. Conservation Evidence, 2, 1–2.

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(2) Ortiz-Catedral, L., Ismar, S., Baird, K., Brunton, D. & Hauber, M. (2009) Recolonization of Raoul Island by Kermadec red-crowned parakeets Cyanoramphus novaezelandiae cyanurus after eradication of invasive predators, Kermadec Islands archipelago, New Zealand. Conservation Evidence, 6, 26 – 30.

12.3.9.

Songbirds

• Two before-and-after trials in the Seychelles (1) and Cook Islands (3) describe population increases in magpie robins and monarch flycatchers following cat and rat control. A beforeand-after study from New Zealand (2) found that the population of South Island robins Petroica australis australis was almost identical before and after rat control. • Two studies (3,5) found higher reproductive success in monarch flycatchers and shrikes in areas with rodent control, compared to areas without control. However, this was climate dependent in shrikes. • A before-and-after study from Hawaii (4) found lower predation on artificial nests after intensive rodent control. A before-and-after study on Frégate (210 ha), Seychelles, between 1981 and 1984 (1), found that the population of Seychelles magpie robins Copsychus sechellarum (a species confined solely to Frégate at the time) increased from 18 to 25 birds following the removal of at least 56 feral cats Felis cattus in 1981–2 and the probable eradication of cats from the island. The authors argue that a reduction in foraging habitat due to agricultural abandonment hindered further population growth. A before-and-after study in 1987– 9 on Breaksea Island (170 ha), South Island, New Zealand (2) found an almost identical number of South Island robins Petroica australis australis after a rat eradication programme as before. This study is discussed in detail in ‘Do birds take bait designed for pest control?’ A paired before-and-after study in Totokoitu Valley, Rarotonga (6,700 ha), Cook Islands (3), found that the nesting success of kakerori (Rarotonga flycatchers) Pomarea dimidiate was significantly higher in areas with an intensive black rat Rattus rattus poisoning programme (62% success for 71 nests in 1988 –93), compared to the same areas in the 1987– 8 breeding season (no nesting attempted) and to other areas without a poisoning programme (26% success for 47 nests in 1987– 93). In areas with rat control adult mortality also fell significantly, from 24% in 1989 –90 to 6% in 1989 –93. The population of kakerori increased from 29 birds in 1989 to 60 in 1993. This study also used nest guards, discussed in ‘Physically protect nests with individual exclosures/barriers’. A before-and-after study on O’ahu, Hawaii, USA, in 1998 (4), found that predation rates on artificial O’ahu ‘elepaio Chasiempis sandwichensis ibidis nests were significantly lower following intensive rodent control compared to before control began. There was a 55% reduction in predation rate for 40 nests placed on the ground and a 45% reduction for 40 nests placed in trees. Egg survival rates over 15 days were approximately 80% following rodent control and 20 – 40% before control. Survival of artificial nests in trees was not significantly different from genuine ‘elapaio nests. Control was through trapping and poisoning (with diphacinone). A controlled, replicated study on San Clemente Island, California, USA, between 2000 and 2006 (5) found that 172 pairs of San Clemente loggerhead shrikes Lanius ludovicianus mearnsi produced 1.1 more fledglings when rodents were controlled in their territories during April– July, compared to control pairs. In drier-than-average years, experimental pairs also raised 1.1 extra fledglings to independence (40 days old). However, there was no effect of rodent control on fledgling success in wetter-than-average years. Management in December–March did not increase either measure of productivity. Rodents were controlled with cholecalciferol rodenticide. This study also investigated the impact of supplementary feeding in addition to rodent control, which is discussed in ‘Provide supplementary food to increase reproductive success’ and the success of captive-bred individuals, in ‘Release captive-bred individuals’. (1) Watson, J., Warman, C., Todd, D. & Laboudallon, V. (1992) The Seychelles magpie robin Copsychus sechellarum – ecology and conservation of an endangered species. Biological Conservation, 61, 93 –106. (2) Taylor, R. H. & Thomas, B. W. (1993) Rats eradicated from rugged Breaksea island (170 ha), Fiordland, New Zealand. Biological Conservation, 65, 191–198.

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(3) Robertson, H. A., Hay, J. R., Saul, E. K. & McCormack, G. V. (1994) Recovery of the kakerori: an endangered forest bird of the Cook Islands. Conservation Biology, 8, 1078 –1086. (4) VanderWerf, E. A. (2001) Rodent control decreases predation on artificial nests in O’ahu ’elepaio habitat. Journal of Field Ornithology, 72, 448 – 457. (5) Heath, S. R., Kershner, E. L., Cooper, D. M., Lynn, S., Turner, J. M., Warnock, N., Farabaugh, S., Brock, K. & Garcelon, D. K. (2008) Rodent control and food supplementation increase productivity of endangered San Clemente Loggerhead Shrikes (Lanius ludovicianus mearnsi). Biological Conservation, 141, 2506 –2515.

12.4.

Control invasive ants on islands

• A replicated, randomised and controlled, before-and-after paired sites study (1) in the USA found temporarily increased fledging success, but no decrease in injuries inflicted by Solenopsis geminata on wedge-tailed shearwaters Puffinus pacificus following ant control. However, there was no change in fledging success or injury rate on an island dominated by the big-headed ant Pheidole megacephala following its eradication, either on the experimental or control island.

Background Several species of ants, including fire ants Solenopsis spp., yellow crazy ants Anoplolepis gracilipes and Argentine ants Linepithema humile have been spread over the world by human activities. Ants are key species in many ecosystems and can have enormous direct and indirect impacts on native species. A replicated, randomised and controlled, before-and-after paired sites study over three breeding seasons in 2002 –2004 on two pairs of offshore islets (25 cm from each nest; the repellent was Arinix™ spiral wrap – a permethrin releasing plastic wrapped around the branch on top of the Tanglefoot. (1) Campomizzi, A. J., Morrison, M. L., Farrell, S. L., Wilkins, R. N., Drees, B. M. & Packard, J. M. (2009) Red imported fire ants can decrease songbird nest survival. The Condor, 111, 534 – 537.

12.24.

Guard nests to prevent predation

Background If populations are reduced to extremely low levels and continue to be threatened by nest predation, then extremely intensive monitoring can be used to ‘guard nests’ and protect nests from predators through direct interference. Due to the intensive nature of this work it is only likely to be viable if there are volunteers to do it, and the population being monitored is very small. Nest guarding can be used as a response to range of threats and is therefore discussed in ‘General responses to small/declining populations’.

12.25.

Use ‘cat curfews’ to reduce predation

• We captured no evidence for the effects of ‘cat curfews’ on bird populations.

Background ‘Cat curfews’ have been started in some cities in Australia, which are aimed at keeping domestic cats Felis catus inside for either the entire day, or during the night, when they do the majority of their hunting.

12.26.

Use lion dung to deter domestic cats

• We found no evidence for the effects of lion dung application on the use of gardens by cats or on cat predation.

Background Lion Panthera leo dung is sold by some companies as a way of deterring domestic cats from entering gardens.

12.27.

Play spoken-word radio programmes to deter predators

• We found no published evidence for the effects of playing the radio on predation rates.

Background An anecdotal account from Abbotsbury Swannery, Dorset, UK, claimed that playing spoken-word radio programmes deterred red foxes Vulpes vulpes from attacking mute swans Cygnus olor.

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Reduce mortality by reducing hunting ability or changing predator behaviour Background In many circumstances it may be unfeasible or undesirable to control predator numbers or exclude predators from areas. However, it may still be possible to reduce the impact of predators in a variety of ways.

12.28.

Use collar-mounted devices to reduce predation

• Two replicated randomised and controlled studies in the UK (1) and Australia (2) found that significantly fewer birds were returned by cats wearing collars with various anti-hunting devices, compared to controls. • A replicated, randomised and controlled study from the UK (1) found no significant differences between different devices. • Both UK studies (1) found that collars were easily lost.

Background Cat collars can be modified to carry either simple bells or more complex sonic alerts which scare birds before cats can catch them. Another option is a ‘bib’ which hangs in front of the cat’s legs, preventing them from hunting effectively. A replicated, randomised and controlled study across the UK between April and August 2002 (1) found that for a total of 89 cats, fewer birds were returned by those fitted with a collar and bell (41% reduction and 74 birds) or a collar with a ‘CatAlert™’ sonic device (51% reduction and 59 birds) than by cats with a plain collar (117 birds). The difference between bell and ultrasound was not significant. A second replicated and randomised study between May and September 2003 found that, for a total of 67 cats, the number of birds returned by cats was not significantly affected by whether cats were wearing collars with one bell, two bells or ‘CatAlert™’ sonic devices. In both trials, the authors note that collars were easily lost, with a total of 55 sonic device, 39 one-bell, 16 two-bell and 21 plain collars lost (and replaced) over the study. The authors also note that that this study does not support the assertion that cats can learn to adapt hunting to render bells less effective. A replicated, randomised and controlled study in Perth, Australia in November–December 2005 (2) found that wearing a ‘CatBib™’ ‘pounce protector’ (a neoprene flap that hangs from a collar in front of a cat’s front legs, acting either as a visual warning or as a barrier to pouncing) for three weeks, reduced the number of cats catching birds by 81% compared to when the same cats were not wearing the ‘CatBib™’ (5 vs. 26; n = 56 cats). The average number of birds captured per cat was also significantly lower (0.29 versus 0.88). Adding a bell to the ‘CatBib™’ did not further reduce hunting. (1) Nelson, S. H., Evans, A. D. & Bradbury, R. B. (2005) The efficacy of collar-mounted devices in reducing the rate of predation of wildlife by domestic cats. Applied Animal Behaviour Science, 94, 273 –285. (2) Calver, M., Thomas, S., Bradley, S. & McCutcheon, H. (2007) Reducing the rate of predation on wildlife by pet cats: the efficacy and practicability of collar-mounted pounce protectors. Biological Conservation, 137, 341– 348.

12.29.

Use supplementary feeding to reduce predation

• A controlled cross-over experiment from the UK (2) found that there was no difference in grouse adult survival or productivity when supplementary food was provided to hen harrier Circus cyaneus compared to in control areas.

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• This study (2) and another from the USA that used artificial nests (1) found that nest predation rates were reduced in areas when supplementary food was provided to predators. A second study from the USA (3) found no such effect.

Background If predators are dependent on threatened birds then providing supplementary food for the predators may remove some predation pressure whilst also supporting the predator population. However, it is also possible that providing supplementary food will allow an increase in the predator population and therefore increase predation pressure. Studies describing the effects of supplementary food on fed populations are described in a separate chapter. A randomised, replicated and controlled experiment on eight Conservation Reserve Program sites in 1993 –94 in Texas, USA (1) found that the predation rates on artificial nests (containing three chicken Gallus gallus domesticus eggs with 1 nest/4.3 ha), were 45% lower in plots where supplementary predator food was provided (details of food provided are not given), compared to nests in control plots. A total of 1,735 artificial nests were used. A controlled cross-over experiment, on moorland in south-west Scotland, UK, in 1998 and 1999 (2) found that adult red grouse Lagopus lagopus scoticus survival was no higher in 13 hen harrier Circus cyaneus territories that were provided with a total of 256 kg of food in spring (over two years), than in control (unfed) territories (78% survival for 94 birds in fed areas vs. 74% of 97 in control areas). Supplementary feeding in the summer (when harriers are provisioning young) reduced the number of grouse chicks being brought to 14 fed broods, compared to ten unfed broods (an average of 0.5 chicks/100 hr, seven in total vs. 3.7 chicks/100 hr, 32 in total). However, there was no corresponding improvement in grouse breeding success in fed areas. A replicated, randomised and controlled study in May–July 2000 in 28 longleaf pine Pinus palustris forest plots in Georgia, USA (3) found no differences in predation rates on artificial nests in areas provided with supplementary food (commercial dry dog food supplied ad libitum from feeders) and control areas (nest predation over one week: 62% for preysupplemented areas vs. 55% for control plots; 770 nests tested). Birds and small mammals were responsible for more predation events in food-supplemented plots, whilst unknown predators were responsible for more in non-supplemented plots. Nests were placed on the ground and contained two Japanese quail Corturnix japonica eggs and one wax covered wooden egg. This study also evaluated the impact of prescribed burning on nest survival, discussed in ‘Use prescribed burning – pine forests’. There was no interaction between feeding and burning. (1) Vander Lee, B. A., Lutz, R. S., Hansen, L. A. & Mathews, N. E. (1999) Effects of supplemental prey, vegetation, and time on success of artificial nests. The Journal of Wildlife Management, 63, 1299 –1305. (2) Redpath, S. M., Thirgood, S. J. & Leckie, F. M. (2001) Does supplementary feeding reduce predation of red grouse by hen harriers? Journal of Applied Ecology, 38, 1157–1168. (3) Jones, D. D., Conner, L. M., Warren, R. J. & Ware, G. O. (2002) The effect of supplemental prey and prescribed fire on success of artificial nests. The Journal of Wildlife Management, 66, 1112 –1117.

12.30.

Use aversive conditioning to reduce nest predation

Background If predators can be taught to associate unpleasant tastes with eggs and/or chicks, then they may stop predating them. This can be achieved either through treating eggs in nests (spraying eggs or the nest) or placing artificial nests in the environment with eggs injected with unpleasant chemicals (not possible with natural nests as it will kill eggs).

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12.30.1.

Avian predators

• Five studies from the USA (1– 3) and Europe (4,7) found reductions in consumption of eggs treated with various chemicals. A further ex situ study from the USA (5) found that American kestrels Falco sparverius consumed fewer chicks when they were treated, but not to the point of losing body condition. • Three studies from the USA (1– 3) found some evidence that treating eggs with some chemicals may have reduced predation of eggs after treatment stopped, or of untreated eggs, although two of these (2,3) were only short term experiments and the third (1) found that the effect was lost after a year. • Four studies from the Europe (4,6,7) and the USA (5) found no evidence for conditioning, or a reduction in predation of wild (untreated) eggs. A randomised, replicated and controlled before-and-after experiment at 21 sites in Illinois and Iowa, USA, in summer 1986 (1), found that predation of dyed-green chicken eggs by American crows Corvus brachyrhynchos over a 23 day period, was significantly reduced when 50% or 100% of green eggs (eight provided each day in total) were treated with Landrin (a tasteless but illness-inducing chemical). There was no corresponding reduction in consumption of green eggs at sites where they were not treated with Landrin. Sites where 12.5% of green eggs were treated had intermediate levels of predation (100% sites: 7.8 attacks/day before treatment vs. 1.2 attacks/day after provision of Landrin-treated eggs; 50% sites: 5.6 vs. 1.4; 12.5% sites: 6.0 vs. 3.4; control sites: 7.6 vs. 7.2). At 50% sites, crows also stopped predating un-dyed eggs and consumption was reduced at 12.5% and 100% sites but remained unchanged at control sites. Post-test trials (when green eggs were again distributed but did not contain Landrin) in 1986 found that crows resumed predation at 100% sites but not at 12.5% or 50% sites. Further tests in 1987 found that crows at all sites except 50% ones resumed predating green eggs. A replicated ex situ trial in the USA (2) found that consumption of Japanese quail Corturnix japonica eggs by 30 fish crows Corvus ossifragus (in five treatment groups) was affected by the injection of different chemicals into the eggs. Topically applying methyl anthranilate to the outside of eggs (alone or in conjunction with injecting 18 mg of methiocarb) reduced consumption compared to other treatments (injection of 18 mg of carbachol or methiocarb or 18 mg methiocarb plus 100 mg methyl anthranilate). Post-treatment tests with untreated eggs found that only crows from the topical methyl anthranilate groups did not consume eggs on the first day following treatment stopping (only two of 12 birds from these two groups resumed consumption in the post-treatment phase, although seven others moved but did not eat eggs). In a separate experiment, 16 crows in two groups were given eggs injected with either 30 mg methiocarb or 40 mg carbachol for five days. These crows consumed more eggs than those exposed to topical methyl anthranilate treated eggs, but fewer than other previous treatments. Five of eight crows exposed to 30 mg methiocarb and three of eight exposed to 40 mg carbachol ate eggs in the post-treatment test period. A replicated, randomised and controlled before-and-after experiment in California, USA, in 1991 (3) found that significantly fewer Japanese quails’ Coturnix japonica eggs were taken by ravens Corvus corax from artificial nest scrapes in a ‘test period’ following a ‘training period’ (approximately two weeks), when eggs were treated with methiocarb than during the training period itself (0 – 33% of eggs taken during the test vs. 9 – 67% during training). Fewer eggs were taken from four sites that contained treated eggs over the test period, compared to sites where eggs were untreated in the test period, but had been treated during training (3% of eggs taken at one of four treated sites only vs. 0 – 33% taken at untreated sites). A follow-up experiment found that one of the eight raven pairs previously conditioned to avoid quails’ eggs resumed predation of eggs (both treated and control eggs) when they were placed in a simulated Californian least tern Sterna antillarum browni colony. A further experiment found that when methiocarb-treated eggs were presented at ten sites within three least tern colonies in 1992, a total of 20 eggs were removed or broken over 1,450 ‘egg days’ and no tern eggs were predated by ravens at any of the colonies in 1992.

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A controlled, replicated before-and-after study at a heronry in northern Italy in 1994 (4) found that the percentage of greenish-brown hens’ eggs predated by hooded crows Corvus cornix was significantly lower than blue hens’ eggs when they were treated with carbachol. There was no difference in predation rates either before or after the 12 day treatment period (before treatment: 100% of both blue and brown eggs consumed within one day, n = 40; treatment: 61% of untreated blue eggs consumed vs. 38% of treated brown eggs, n = 480; after treatment: 90% of both blue and brown eggs consumed, n = 40). During the conditioning period, consumption rates were similar until the tenth day and then only a single brown egg was consumed over three days. A replicated, randomised and controlled ex situ experiment with 33 American kestrels Falco sparverius (5) found that control (untreated) day-old chicks were preferentially chosen, compared with chicks treated with methyl anthranilate on two out of four experimental days (ten birds choosing controls first vs. one choosing methyl anthranilate treated chicks and nine choosing controls vs. two choosing treated). Birds showed a preference for controls over aminoacetophenone-treated chicks on one day (nine choosing controls vs. two choosing treated chicks). On all other days there was no difference in preference for treatment or control chicks. The total amount of food consumed was highest for control kestrels, intermediate for those fed on aminoacetophenone-treated chicks and lowest for those fed methyl anthranilatetreated chicks, however, kestrels did not appear to lower consumption to the point of threatening body condition: there were no significant differences between kestrel weights at the end of the trial. A further replicated, randomised and controlled experiment found that treating cockerels with the two chemicals and dyeing them either green or blue greatly reduced food intake. However, there was no difference between consumption of dyed and treated chicks and controls that were only dyed, suggesting that aversive conditioning was not occurring. This study is also discussed in ‘Use coloured baits to reduce accidental mortality during predator control’ and ‘Use repellents on baits’. A controlled before-and-after study in a least tern Sterna albifrons colony in west Portugal (6) found that 15 artificial nests containing methiocarb (an illness-inducing chemical) treated quails’ eggs were predated by carrion crows Corvus corone at the same rate as 15 artificial nests containing untreated quails’ eggs. During pre-treatment (no eggs treated), first treatment phase (six days with treated eggs in experimental nests and untreated eggs in control nests) and second treatment phase (a further eight days of treatment) all eggs were destroyed within 24 hours of placement, although many treated eggs were not consumed following removal. A replicated before-and-after study on Vila Islet, Azores, Portugal, in 2003 (7), found that the number of methiocarb-treated domestic quails’ Coturnix coturnix eggs (11.25 mg methiocarb/egg) predated by yellow-legged gulls Larus michahellis from artificial tern nests in a mixed common tern Sterna hirundo and roseate tern S. dougalli colony, over six days was significantly lower than the number of untreated eggs taken in the previous three days (2.5 treated eggs predated/day vs. 10.6 untreated eggs predated/day). Once terns started laying, treated eggs were placed in 18 artificial nests at the colony and replaced if predated. No gulls were observed removing eggs over 13 days, but European starlings Sturnus vulgaris took both treated eggs and tern eggs. Predation of treated eggs declined over time, but there was no corresponding decline in predation on genuine tern eggs (days 1– 6: 13% of tern eggs and 9.3% of treated eggs predated; days 7–13: methiocarb concentration increased to 22.5 mg/ egg, 12.3% of tern eggs predated vs. 5.6% of treated eggs). (1) Dimmick, C. R. & Nicolaus, L. K. (1990) Efficiency of conditioned aversion in reducing depredation by crows. Journal of Applied Ecology, 27, 200 –209. (2) Avery, M. L. & Decker, D. G. (1994) Responses of captive fish crows to eggs treated with chemical repellents. The Journal of Wildlife Management, 58, 261–266. (3) Avery, M. L., Pavelka, M. A., Bergman, D. L., Decker, D. G., Knittle, C. E. & Linz, G. M. (1995) Aversive conditioning to reduce raven predation on California least tern eggs. Colonial Waterbirds, 18, 131–138. (4) Bogliani, G. & Bellinato, F. (1998) Conditioned aversion as a tool to protect eggs from avian predators in heron colonies. Colonial Waterbirds, 21, 69 –72.

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(5) Nicholls, M. K., Love, O. P. & Bird, D. M. (2000) An evaluation of methyl anthranilate, aminoacetophenone, and unfamiliar coloration as feeding repellents to American kestrels. Journal of Raptor Research, 34, 311– 318. (6) Catry, T. & Granadeiro, J. P. (2006) Failure of methiocarb to produce conditioned taste aversion in carrion crows consuming little tern eggs. Waterbirds, 29, 211–214. (7) Neves, V. C., Panagiotakopoulos, S. & Furness, R. W. (2006) A control taste aversion experiment on predators of roseate tern (Sterna dougallii) eggs. European Journal of Wildlife Research, 52, 259 –264.

12.30.2.

Mammalian predators

• One study from the USA (1) and three ex situ experiments (2 – 4) found evidence for lower consumption of eggs treated with repellent chemicals. • However, when untreated eggs were provided simultaneously with (1) or after (2 – 4) treated eggs, no studies found evidence for continued lower predation. I.e. aversive conditioning did not occur. In addition, a study from the USA (5) found no effect of repellent chemicals on predation rates of genuine nests. A replicated and controlled before-and-after experiment in southern Connecticut, USA, in June–September 1986 (1), found that distributing 40 eggs treated with 20 –25 mg of emetine dihydrochloride along 0.7–1.0 km transects at three second growth deciduous forest sites each week for three weeks reduced consumption of eggs by mammalian predators (raccoons, opossums, skunks and rodents) by >80% during treatment and for the following three week period (from >75% of eggs predated daily to