Chimney Swift Towers: New Habitat for America's Mysterious Birds [1 ed.] 9781603445900, 9781585443727

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Chimney Swift Towers

NUMBER THIRTY-EIGHT

Louise Lindsey Merrick Natural Environment Series

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Building Chimney Swift Towers

Chimney Swift Towers

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New Habitat for America’s Mysterious birds

A Contruction Guide By PAUL D. KYLE and GEORGEAN Z. KYLE

TEXAS A & M UNIVERSITY PRESS College Station

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Building Chimney Swift Towers

Copyright © 2005 by Paul D. Kyle and Georgean Z. Kyle Manufactured in China by Sun Fung Offset Binding Co., Ltd. All rights reserved First edition

The paper used in this book meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials, Z39.48-1984. Binding materials have been chosen for durability.

Library of Congress Cataloging-in-Publication Data Kyle, Paul D., 1950– Chimney swift towers : new habitat for America’s mysterious birds / by Paul D. Kyle and Georgean Z. Kyle. p. cm.—(Louise Lindsey Merrick natural environment series ; no. 38) ISBN 1-58544-372-7 (pbk. : alk. paper) 1. Chimney swift—Housing.

2. Towers—Design and

construction. I. Kyle, Georgean Z., 1950– II. Title. III. Louise Lindsey Merrick natural environment series ; no. 38. QL696.A552K95 2005 639.9'78762—dc22

2004011787

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Contents 7

Preface

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Introduction

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An Overview of the Chimney Swift

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Tower Construction Basics

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Wooden Towers

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Building a 12 Ft. Freestanding Tower

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Building a Kiosk Tower

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Other Wooden Tower Designs

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Masonry Towers

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Building a Chimney Swift Castle

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Other Masonry Tower Designs

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A Conservation Plan Using Multiple Towers

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Monitoring Roost and Nest Sites

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Site Report Form

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Building Chimney Swift Towers

Preface

Preface W

HEN ALTHEA ROSINA SHERMAN built the original Chimney Swift tower in 1932, she could not have foreseen the interest in or the need for additional structures of similar design. Her quest for knowledge about the small, sleek, littleknown bird was the seed that has grown into a continent-wide education and conservation effort. In our book Chimney Swifts: America’s Mysterious Birds above the Fireplace, we introduce North Americans to Chimney Swifts as well as to the concept of maintaining and creating habitat for these unique and beneficial birds. In this book, we provide guidance to those individuals who wish to go beyond simply keeping existing chimneys open and clean for the purpose of Chimney Swift conservation. Anyone with basic woodworking or masonry skills and an interest in wildlife conservation will find this publication helpful, including do-it-yourselfers, homeowners involved in creating backyard habitat for wildlife, landscape and structural architects, park and wildscape managers, wildlifemanagement-area professionals, nature centers, garden centers, and Eagle Scouts in search of community service projects. Althea Rosina Sherman with a group of visitors and her “Chimney Swifts’ tower.” Courtesy Oberlin College Archives, Oberlin, Ohio

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Chimney Swifts going to roost.

Preface

Introduction T

HE TREND in migratory bird populations in North America is not a positive one. Breeding-bird surveys continue to indicate that the numbers of many neotropical migrants are in decline, and Chimney Swifts are no exception. The conservation of some species is more difficult than others, and that difficulty is often determined by the amount of habitat that must be preserved. In the case of the Chimney Swift, the necessary habitat is mostly open sky—something that is still quite abundant. But even the ever-flying swifts must return to earth to roost each night, build their nests, and raise their young. What they need takes up very little space. They need an interior shaft that is deep, dark, open on the top, and roughly textured on the inside. Historically, that has been a large, hollow tree. Today, swifts use chimneys and other similar human-made structures. Humans have become proficient at building chimneys for their own use, and Chimney Swifts have taken full advantage. They followed our westward progress across North America, and their once-eastern population currently extends more than halfway across the continent. But something has changed, and it is affecting Chimney Swift populations in a very different way. Many masonry chimneys are being capped and others torn down in favor of new construction. The new chimneys are often lined with steel rather than brick, making them useless to the swifts. Humans have inadvertently created enough new habitat that a beneficial, insect-eating species

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Introduction

such as the Chimney Swift has actually flourished, so it should be possible to purposely create habitat specifically for them. The once-diminished bluebird and Purple Martin populations have been increased with the use of “artificial” housing. Why not the Chimney Swift population? Our own interest in Chimney Swifts began in 1983 when, as neophyte birders, we “discovered” the species. An occasion to handle an adult Chimney Swift allowed us to see the unique characteristics of swifts: long graceful wings, spiny tail, extremely strong grip, and incredibly captivating eyes. Our curiosity led us to Richard Fischer’s Breeding Biology of the Chimney Swift (University of the State of New York, 1950), Ralph Dexter’s many scientific papers in Auk, Bird-Banding, Wilson Bulletin, and others on the roosting behavior of Chimney Swifts in the air shafts on the campus of Kent State University, and finally to the writings of Althea Sherman. In her 1952 book, Birds of an Iowa Dooryard (Christopher Publishing House, 1952), she describes a “Chimney Swifts’ tower” that was constructed for the purpose of studying the home life of swifts. In 1989, we constructed two Chimney Swift towers of our own as an integral part of our home. Based loosely on Sherman’s design, these 22 ft. structures allowed us to observe Chimney Swifts firsthand. The towers were occupied by swifts the first year they were in place. Our intimate observations of the birds initiated a profound concern for the future of this remarkable species. In 1995, under the auspices of the Texas-based Driftwood Wildlife Association, the North American Chimney Swift Nest Site Research Project (NSRP) began as an effort to promote Chimney Swift conservation by the following methods:

Introduction

• Identifying and monitoring existing nest and roost sites • Educating property owners about the beneficial nature of Chimney Swifts as insectivores • Designing, installing, and monitoring new structures specifically for use by Chimney Swifts as nest and roost sites The original goal of the project was to design a Chimney Swift tower that could be easily built and installed by a homeowner with average do-it-yourself construction skills. We constructed dozens of towers of different specifications and gathered feedback from the experiences of other research associates all across North America. Initial results were mixed, but we have found several designs that appeal to Chimney Swifts as nesting and roosting sites that are affordable, attractive, and relatively easy to build with readily available materials. The designs described in this construction guide are some that have proven to be the most successful to date.

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An adult Chimney Swift in flight.

Overview

An Overview of the Chimney Swift T

O UNDERSTAND THE HABITAT requirements of Chimney Swifts, it is important to know something of their character, behavior, and breeding biology. Family: Apodidae Genus and species: Chaetura pelagica Length: Overall body length, about 5 inches Wingspan: Extended wings, 12–12½ inches tip to tip Weight: Average adult weight, 22.8 grams Color: Sooty gray to bluish black with a lighter gray throat; male and female identical in appearance Description of flight: Soar on long, scytheshaped wings, with a stubby tail that spreads when turning sharply while feeding; abrupt, jerky, batlike flight due to short, relatively massive upper wing bones; flight presents the illusion of wings flapping alternately (disproved by stroboscopic photography) Voice: Adults: a sharp, rapid “tick-tick-tick” or bright “chippering” sound Young feeding call: a raucous “gim-me, gimme, gim-me” Young alarm call: a winding or whirring “raah, raah, raah”

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Young swifts may also “sing”: a soft, rhythmic “peeping” in dramatic contrast to their more well known vocalizations Description at rest:Unable to perch or stand; cling, facing upward, to vertical surfaces; center spines on tips of the tail exposed like needles and used to prop against vertical surfaces; long wings cross over the rump by an inch or more Temporal presence: Arrive in southern United States in mid-March; arrive in Canada by May; depart northernmost range by September and southernmost range by mid- to late October Range: North American winter months: reside in upper Amazon basin of eastern Peru, northern Chile, and northwestern Brazil; full extent of their southern range unknown Summer breeding season: along the east coast of North America from southern Florida northward to Nova Scotia; westward from south Texas northward to southeastern Saskatchewan Nesting period: May through August Number of broods: One brood per season most common; two broods regularly documented in southern areas of breeding range Nesting location: Known to nest inside hollow trees, chimneys, air shafts, silos, wells, sinkholes, outbuildings, and structures built specifically for their use; only one nest per season constructed in any location, regardless of the size of the site Nest: Locally available items, such as small dead twigs or pine needles, gathered in flight from the tips of standing trees by grasping with the feet; selected matter snapped off and transferred to the bill; in the nesting site, the material is glued to the inside of the vertical

Chimney Swifts at rest.

Range map. The breeding range of Chimney Swifts in North America has been well documented and is represented on the map by the shaded area. The “date lines” indicate some typical first sightings in the spring. The southern range of Chimney Swifts is less well understood. The center point indicates the location where Chimney Swifts banded in North America were first recovered in 1944. The arrows radiating from this point indicate Chimney Swift sightings and the possible extent of their winter range in South America.

Overview

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Eggs in a nest. shaft with the swifts’ saliva; average nest contains about 265 individual pieces; built by both parents Width: 3½–4¼ inches Height: 1–1¼ inches Distance from the wall: 1⅞–3 inches Eggs: Clutch of 2–7 white eggs (3–5 most common); female deposits an egg every other day, usually just before dawn; eggs measure ¾ × ½ inch Incubation: 18–21 days by both parents, alternating

One-day old hatchling.

Overview

Eight- to ten-dayold nestlings.

Brooding of young: By both parents, alternating Feeding of young: By both parents on average every 30 minutes until the young are 7 days old; averaging hourly thereafter; not unusual

Fourteen-dayold nestlings.

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for “helpers” (usually one-year-old swifts) to assist in feeding the young after the young are about 1 week old Hatchlings/nestlings: Altricial (blind, naked, helpless) with proportionally large feet with sharp claws 3 days: feather tracts visible on the back and wings 10 days: wing feathers begin to unfurl 14 days: eyes begin to open; milky blue in color; lids wrinkled Fledglings: 20 days: eyes have turned brown; fully feathered; “practice flapping” by holding tightly to the nest and exercising their wings until out of breath 21–26 days: flying up and down inside the chimney or tower like miniature helicopters 28–30 days: first flight outside the chimney or tower Diet: Prey captured in flight; primarily small flying insects less than 0.2 inch in length; insects taken include mosquitoes, midges, flies, spittlebugs, aphids, winged ants, tiny bees and wasps, mayflies, stoneflies, and termites; opportunistic feeders; single Chimney Swift will eat more than 1,000 mosquito-sized insects each day Roosting behavior: Congregate in flocks of hundreds and even thousands at suitable roost sites; large flocks most commonly form during spring and fall migration Longevity: Average 3–5 years; oldest known individual more than 14 years old Ecological status: Numbers declining since mid1980s

Twenty-one-day-old fledgling.

Tower Construction Basics

Tower Construction Basics W

HEN CONSTRUCTING TOWERS specifically for use by Chimney Swifts as nesting and roosting sites, you must take into account the following factors. Diameter: The tower must be large enough in diameter for the swifts, with their 12–12½ in. wingspan, to be able to fly up and down inside the structure. Although some experimental 12 in. cinderblock towers have been successful, we now consider a 14 in. minimum inside diameter to be preferable in wooden towers. Wooden towers must be larger to compensate for their susceptibility to overheating. Height: The tower must be deep enough (8 ft. minimum) to provide protection of the nest from direct sunlight. Small towers (8–12 ft. tall with 14– 18 in. inside diameter) are suitable for use as nest sites. Larger towers are also more likely to be used as roosts by substantial numbers of nonbreeding and migratory Chimney Swifts. Top opening: The width of the top opening of the tower should be no more than half the inside diameter. The opening should be situated on the north top edge of the tower to limit the amount of

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rain and direct sunlight that is able to penetrate inside the tower. For example, the top opening for a 14 × 14 in. tower should be no more than 7 × 14 in. Bottom ventilation: Air must be able to move up the tower to prevent it from overheating. A grid of holes no larger than ⅜ in. will provide adequate circulation without allowing access to snakes. A removable bottom will facilitate cleaning at the end of the nesting season. Insulation: Because Chimney Swift Towers are not surrounded by a house as regular chimneys are, they are subject to overheating. We highly recommend using double-walled structures to minimize this problem. This means that the nest chamber should be separated from the outside wall by an insulated space. This space should be a minimum of ¾ in. and filled with ¾ in. rigid insulation board. Even in cooler climates, insulation will help moderate the temperature inside a tower. Inside material: The inside surface must have enough texture for the swifts to be able to cling to the vertical surface. Unpainted, rough-textured exterior wood siding, cinder block, textured concrete, or rough-textured stucco work well. Outside material: This must be durable, heat reflective (light in color), and difficult for predators to climb (smooth textured). The most important lesson we have learned in our search for the perfect Chimney Swift tower is that even the best of our smaller designs to date cannot duplicate the ideal nesting conditions provided by a small masonry chimney. Chimney Swift towers should be built as additional habitat, not as

A typical Chimney Swift tower.

Tower Construction Basics

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replacements for chimneys being used successfully by nesting and roosting swifts. Like building housing for a Purple Martin colony, constructing even a small Chimney Swift tower requires a considerable investment of time and resources. However, when a pair of swifts accepts one of these structures, it will become more than just a nest box for raising their young. Unlike many other species of cavity-nesting birds that abandon the nest site when the nestlings fledge, Chimney Swifts continue to use their chosen site as a nightly roost throughout the spring and summer and into the fall. It also serves as a refuge from inclement weather and a safe place to rest during intense summer heat or when flying insect food is scarce; it is literally their only terrestrial contact. In a very real sense, an occupied tower will become “home” to the resident birds during their entire six- to seven-month stay in North America. A Chimney Swift tower is an investment that can add to the landscape architecture of a home as well as provide years of enjoyment. Individuals who construct new Chimney Swift habitat may have the opportunity to witness a unique behavior. When a new tower is first discovered by a swift, the bird will utter very loud, continuous, excited chippering while inspecting the structure. Beginning at the top of the tower, the swift will make passes from every conceivable angle, stall over the top, and peer inside. It will then make flybys lower and lower until skimming a mere two feet from the ground, still vocalizing and approaching each side of the structure from different directions. Following the exterior inspection, the bird will circle above the tower, raise its wings, and disappear inside. The tower will be inspected, approved, and claimed in less than five frenetic minutes.

Tower Construction Basics

In instances where we have had the privilege to observe this behavior, the swifts have appeared to be totally oblivious to our presence. Their entire focus was on the tower as a potential nesting site. Like a child’s on Christmas morning, their enthusiasm is explosive. Remarkably, this behavior is usually displayed only once. As soon as a tower has been discovered, it enters into the “neighborhood registry.” Occupants will change over the years, but the excited display of the original discovery may never be repeated.

Selecting a Tower Site Proper placement and installation will play a critical role in making a tower attractive to Chimney Swifts. The first consideration when choosing a site is the accessibility of the tower to the swifts. Because Chimney Swifts have adapted to associate “home” with human structures, it may be advantageous to consider a site that is in close proximity to some type of building. Chimney Swifts are known to use chimneys that are under tree canopies. However, a new site may be found more quickly if it is located in an area that is open to the sky. The second area of concern should be the safety of the swifts if they do choose to move into the tower. A safe tower must be located where mammals such as tree squirrels, raccoons, and cats cannot jump to the top of the structure. To minimize this problem, make certain that the top of the tower is at least 10 ft. from surrounding tree branches and other structures. If the tower is attached to an existing structure, it should extend at least 4 ft. above that structure. Because overheating can present a danger to

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Chimney Swifts—especially to a nest of eggs, hatchlings, or young birds that are not yet capable of flight outside the nest tower—proper construction alone may not be sufficient. Whenever possible, locate the tower north and east of trees or structures to provide shade protection from the summer sun, especially in the afternoon when temperatures are at their peak. Finally, wherever the tower is located, it must be stable. Chimney Swift towers can be freestanding or attached to an existing structure, such as a house, fence, or outbuilding. Freestanding towers are easier to protect against mammalian predators and ants, but they will require the construction of a concrete foundation. As a general rule, 8 ft. tall towers require a foundation measuring at least 36 × 36 × 6 in. thick. Towers that are 12 ft. tall require a foundation measuring at least 48 × 48 × 9 in. thick. All concrete foundations should contain two layers of steel remesh or a double grid of ⅜ in. rebar for strength. Special consideration should be given to foundation construction in colder climates where frost heave may be a concern.

Protecting against Predators Proper site selection and installation will eliminate most predator problems if the outside of the tower is too smooth for mammals and reptiles to climb. However, if wood siding is used on the outside, it is best to fit the tower with a predator guard. This is simply a 24 in. band of metal flashing that wraps around the top of the tower. During the summer nesting season, efforts should be made to keep vegetation low around the tower foundation. Tall grasses and other plants that come into contact with the tower can provide “highways” for ants that can overrun a nest and

Tower Construction Basics

devour the nestlings. If a tower is built on legs, a 2–3 in. band of sticky insect barrier such as Tanglefoot should be applied to each leg near the base of the tower. It should be inspected several times during the nesting season for effectiveness. In towers that are in direct ground contact, a dusting of diatomaceous earth or 5 percent Sevin dust around the base of the tower will help keep ants away from the nest. Treatment will need to be reapplied periodically if ants are seen, and especially after rainstorms.

Tower Maintenance Chimney Swift landlords should perform no maintenance or intrusive activities in or around the towers during the time that Chimney Swifts are in residence. This is quite different than the interactive care required for Bluebirds and Purple Martins. In the fall, after the Chimney Swifts are no longer using the tower, the bottom should be cleaned of droppings, eggshells, and other material. Ideally, the nest from each season should also be removed before the swifts return. Although Chimney Swifts have been observed reusing an old nest, it will not be as structurally strong and secure as a newly constructed one, and nest building seems to be an important part of pair bonding in Chimney Swifts. After cleaning the bottom of a freestanding tower, make certain the bottom is securely reattached. The outside walls of towers that are sided with wood will need to be repainted every few years, either before the swifts arrive or after they leave. Covering the top during the winter will extend the life of wooden towers. The inside walls of cinderblock towers will need to be retreated with a latex-based sealer every year.

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Wooden Towers

Wooden Towers A

LTHOUGH CHIMNEY SWIFTS currently nest most commonly in masonry chimneys and air shafts, they evolved to nest in hollow trees. Therefore, their saliva is best suited to gluing their nests to wood—untreated, unpainted wood. Ornithologists and conservationists have experimented with many sizes and shapes of wooden Chimney Swift towers for nearly a century. Some have been as small as 1 ft. square and no more than 4 ft. tall, whereas others have measured more than 2 ft. in diameter and stood 20 ft. or higher. Our own experiments have included several 11 × 11 in. × 8 ft. towers. In general, the larger towers have been more consistently successful in producing fledged young. In some specific situations, the smaller towers have been successfully used as nest sites by Chimney Swifts. However, these “minitowers” have also had a large number of failed nests due to overheating. Based on more than a decade of experimentation, we have determined the minimum size for a wooden Chimney Swift tower to be approximately 14 × 14 in. × 8 ft. tall. But 12 ft. tall towers are highly recommended. These dimensions take into account both the needs of the swifts and the most economical use of readily available materials. Our material of choice for the inside of wooden towers is a product called Textured One-Eleven (T1-11). It is a rough-textured, exterior plywood product that is commonly used as siding on buildings. It is available in 4 × 8 ft. sheets and in two

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thicknesses, ⅜ in. and ⅝ in., but only the ⅝ in. T111 is appropriate for towers. The thicker T1-11 is available with deep grooves every 4, 8, or 12 in., which make excellent footholds for Chimney Swifts when installed horizontally. We recommend the product that has grooves every 4 in. The thinner ⅜ in. material does not have the deep grooves, and the surface has less texture and will quickly become too smooth for the swifts to grip.

Building a 12 Ft. Freestanding Tower This tower can be built using basic tools: hammer, lumber crayon, carpenter’s square, framing level, hacksaw, circular saw, power screwdriver/drill, table saw, and cement mixer. Some lumber supply companies may have the facilities for precutting some of the plywood parts, thereby eliminating the need for a table saw.

Materials 4 × 8 ft. × ⅝ in. Textured One-Eleven (T111) siding (nesting chamber) (2 sheets) 1¼ in. exterior deck screws (nesting chamber assembly) (2 lb.) 2 in. deck screws (sun collar and cleat attachment) (30) 3 in. deck screws (form box assembly and bracing) (30) #10 × ¾ in. hex washer self-drilling metal screws (tower leg attachment) (40) 2 × 10 in. × 8 ft. construction lumber (concrete foundation form) (2) 2 × 4 in. × 8 ft. construction lumber (temporary brace boards) (2) 2 × 4 × 18 in. stakes (form and tower base stabilizers) (6)

Wooden Towers

Completed tower with a metal predator guard. 40 in. pieces ⅜ in. rebar and tie wire (foundation) (16) 12 in. pieces ⅜ in. rebar and tie wire (foundation) (8) ¾ in. pressure-treated, exterior plywood measuring: 15 × 15 in. (tower bottom) (1) 17¼ × 17¼ in. (tower top) (1) 7 × 8 in. (sun collar) (2) 13½ × 8 in. (sun collar) (2)

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1½ × 1½ in. pressure-treated lumber (cleates for tower top and bottom) (8 ft.) 1½ × 1½ × ⅛ in. angle steel measuring 5 ft. long (tower legs) (4 pieces) 80 lb. bags of gravel-mix concrete (foundation) (approximately 20) 1 × 4 in. × 12 ft. pressure-treated lumber (corner braces/spacers) (11 pieces) spray primer (enamel) (tower legs) (1 can) spray paint (enamel) (tower legs) (1 can) ¾ in. foil-backed, rigid, foam insulation board (2 sheets) siding and trim/edge flashing/predator guard flashing (these will vary depending on the type of siding used for the exterior of the tower)

Construction of the Foundation Form Materials 2 × 10 in. × 8 ft. construction lumber (2) 3 in. deck screws 2 × 4 × 18 in. stakes (4) Step One Cut each piece of 2 × 10 in. lumber into one 48 in. and one 45 in. piece. Step Two Using the 3 in. deck screws, construct a form box from the lumber measuring 48 × 48 in. This will be used as a form for pouring the foundation. Step Three Place the form box on the tower site oriented in the desired position. Mark the area, and remove the form box. Excavate a flat-bottomed square hole that is approximately 60 in. square and 3 in. deep.

Wooden Towers

Step Four Place the form box in the excavated area. Secure the frame in a square, level position with at least four substantial wooden stakes and 3 in. deck screws. The Interior Tower Sections (Nesting Chamber) Materials 4 × 8 ft. × ⅝ in. T1-11 siding (2 sheets) 1¼ in. exterior deck screws Step One The edges of T1-11 are designed to overlap when installed as siding. Therefore, the two long edges are different. To facilitate construction and to avoid confusion, mark the sheets for future reference. Lay the siding flat with the grooves facing down, and place a mark every 16 in. along the 8 ft. length of the back of each sheet. Using a lumber crayon or other bold marking device, draw an arrow between each of the initial marks that point to the rabbeted (or notched) edge (see Figures 1a and 1b). Step Two Using a circular saw, crosscut both sheets into 48 × 48 in. sections. Step Three For best results, use a table saw for steps three and four, and place the “factory edge” next to the saw fence. Crosscut two of the 48 × 48 in. sections into 6 strips measuring 15¾ in. Make certain that all cuts are perpendicular to the grooves (see Figure 1a). Mark all six strips with a “W” for “wide.” Step Four Crosscut the remaining 48 × 48 in. sections into

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six strips measuring 14⅝ in. Make certain that all cuts are perpendicular to the grooves (see Figure 1b). Mark all of these strips with an “N” for “narrow.”

Step Five Using the 1¼ in. deck screws, assemble three boxes measuring 48 × 15¾ × 15¾ in. Each box should be assembled with the grooves facing inward and the arrows all pointing in the same direction. Use two “W” and two “N” strips for each box (see Figures 2 and 2a). Caution: Be certain that no screws protrude into the interior of the boxes. If assembled properly, the three tower sections will stack and interlock to form a structure measuring 15¾ × 15¾ in. × 12 ft. tall. Preparation and Installation of the Bottom Tower Section Materials ¾ in. pressure-treated, exterior plywood measuring 15 × 15 in. 1½ in. × 1½ in. pressure-treated lumber (8 ft.) 2 in. deck screws 3 in. deck screws 1½ × 1½ × ⅛ in. angle steel measuring 5 ft. long (4 pieces) #10 × ¾ in. hex washer self-drilling screws 2 in. × 4 in. × 8 ft. construction lumber (2) 2 in. × 4 in. × 18 in. stakes (2) 40 in. pieces of ⅜ in. rebar and tie wire (16) 12 in. pieces of ⅜ in. rebar and tie wire (8) 80 lb. bags of gravel-mix concrete (approximately 20) spray primer and spray paint

Wooden Towers

Tower section assembly.

Step One Choose one section to be the bottom. Trim the rabbeted edge off one end so that the walls on the end of the section measure ⅝ in. thick. Cut two pieces 14½ in. long and two pieces 117/16 in. long from the 1½ × 1½ in. lumber. Using the 2 in. deck screws, install these pieces as cleats on the inside and even with the trimmed end of the tower section. Drive the screws through the outer walls of the section into the cleats. It is helpful to use clamps to hold the cleats in place while installing the screws.

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Installing cleats in the bottom tower section.

Installing the tower bottom.

Wooden Towers

Step Two Drill a grid of ⅜ in. holes, 1⅜ in. apart, in the 15 × 15 × ¾ in. plywood for ventilation (see Figure 3). Install this piece to the cleated bottom section with four of the 2 in. deck screws. Step Three Prime and paint the angle steel to help prevent rust and corrosion of the legs. Install a 5 ft. piece of angle steel on each corner so that 3 ft. of the steel extends beyond the cleated end of the bottom tower section. These will be the legs of the tower. Use the self-drilling screws and a power screwdriver, or predrill the angle steel. Space the screws about 6 in. apart. Be certain that no screws protrude into the interior of the tower section. Step Four Stand the bottom tower section in the center of the foundation form box. Secure the bottom section in a perfectly vertical position using a framing level, 2 × 4 in. × 8 ft. brace boards, 18 in. stakes, and 3 in. deck screws. Install a two-layer grid of ⅜ in. rebar (spaced approximately 10–12 in. on center). Drive the 12 in. pieces of rebar into the ground 6 in. from the side of each form board and centered on each side. The rebar should be 1 in. below the top edge of the form box. Use tie wire to attach the grid of ⅜ in. rebar horizontally inside the form box. The steel legs should be wired to the ⅜ in. rebar for additional strength. Step Five Thoroughly dampen the soil inside the form box, and fill the form box to the top with properly mixed gravel-mix concrete (follow the instructions on the bag).

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Step Six Recheck the bottom tower section with a level, and carefully adjust if necessary. Once the concrete has set, keep the foundation moist by covering with old dampened blankets, empty concrete bags, or burlap bags. Allow the covered foundation to cure for forty-eight hours before removing the forms or continuing with construction. Completing the Nesting Chamber Materials 1 × 4 in. × 12 ft. pressure-treated lumber (11 pieces) 1¼ in. deck screws 2 in. deck screws ¾ in. pressure-treated plywood measuring: 17¼ × 17¼ in. (1) 7 × 8 in. (2) 13½ × 8 in. (2)

Tying steel in the foundation.

Wooden Towers

Completed tower base and foundation.

Step One Remove the bracing from the bottom tower section, and place one of the two remaining sections on the base section. Make certain that the arrows on both sections point in the same direction, or they will not interlock. The section may need to be tapped into place. Step Two Cut eight pieces of the 1 × 4 in. lumber into sixteen pieces measuring 6 ft. each. Notch eight of the 6 ft. pieces to fit around the angle steel legs that are attached to the bottom section (see Figure 4).

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Interlocking tower sections.

Step Three Use 1¼ in. deck screws to secure the notched 1 × 4 in. pieces over the corners of the bottom and middle sections. They should be even with the bottom and extend halfway up the middle section. Once all eight corner pieces are installed, a ladder can be safely leaned against the middle section for access to the final section. Caution: Do not use screws longer than 1¼ in. They will protrude into

Wooden Towers

the nest chamber and cause a serious hazard for the swifts.

Step Four Install the final section on top of the tower. Step Five Install the remaining 1 × 4 in. pieces on the corners of the tower. Once this step is completed, the tower will be completely self-supporting.

Installing notched corners.

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Installing top tower section.

Tower top with sun collar.

Wooden Towers

Installing insulation in the air space.

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Step Six Using eight of the 2 in. deck screws, assemble the smaller pieces of treated ¾ in. plywood into a box that measures 8½ × 13½ × 8 in., and sand the edges smooth. This will be a “sun collar” for the top of the tower to limit the amount of sunlight that enters the nest chamber. Step Seven Cut an offset hole in the 17¼ × 17¼ in. piece of pressure-treated plywood that measures 6 × 11 in. (see Figure 5). Sand the edges of the hole smooth. Use 2 in. deck screws to install the sun collar over the hole. Center the complete unit over the top of the tower with the sun collar on top. Note: Place the hole and sun collar on the northern edge of the tower. This will provide the most protection to the interior of the nest chamber from direct sunlight. Secure the top with eight evenly spaced 2 in. deck screws. Sheathing and Trimming Out the Tower By installing sheathing over the 1 × 4 in. corner strips, a ¾ in. air space is created between the outside wall and the interior nesting chamber. This will help keep the inside of the tower from overheating. Filling the air space with ¾ in. rigid foam insulation board (with the foil side out) prior to sheathing is highly recommended. A variety of products may be used for sheathing. It may be painted or stained to match nearby structures. Light colors are recommended to keep the tower cool. Trim boards on the corners and around the top will give the tower a finished and more appealing look. Several of our associates have used vinyl siding on the outside of their towers, and we have also

Wooden Towers

experimented with this material. It has a number of definite advantages over wood siding: it is too slick for predators to climb—eliminating the need for a predator guard; it provides an additional air space—keeping the nest chamber cooler; and it never needs painting. Another product that works well is Hardipanel. This is a composite material that is too slick for predators to climb and essentially maintenance free.

Installing the Predator Guard Once the sheathing and trim are in place, install the predator guard. This can be a 24 in. piece of

Installing sheathing.

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metal flashing wrapped around the top of the tower or separate panels of metal attached to all four sides. Screws used to attach the predator guard should be flush with the surface, leaving the top 24 in. of the tower as slick and smooth as possible.

Figure 1a

Figure 1b

Figures 1a and 1b. T1-11 nest chamber section layout.

Wooden Towers

Figure 2. Nest chamber section: side view.

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Figure 2a. Nest chamber section: top view.

Wooden Towers

Figure 3. Tower bottom.

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Figure 4. Tower base detail.

Wooden Towers

Figure 5. Tower top.

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Building a Kiosk Tower A Chimney Swift tower can catch the eye of people as well as house-hunting swifts. This is especially true when the tower is placed in a high-traffic area such as a park. This presents an excellent opportunity to educate the public about Chimney Swifts. However, the attention of curious humans, their children, and their pets can create enough activity around the tower to interfere with nesting activities. A good solution to this problem is a Kiosk Tower. This design was first built at the Center for Environmental Education in Austin, Texas. The nest chamber was based on our time-tested 12 ft. towers built of T1-11 siding. Kiosk panels measuring 4 × 4 ft. were fitted on all sides. The kiosk panels A Kiosk Tower. This tower is surrounded by a butterfly garden that is maintained by the Ridgelea Neighborhood Association in Austin, Texas.

Wooden Towers

and the lower half of the tower are sheltered by a roof. The roof and panels provide additional protection from the often relentless summer sun and prevent visitors from inadvertently disturbing the nest chamber. In addition, the panels provide an ideal place to mount educational visual displays. The tower was successfully used by nesting Chimney Swifts the first season and every year thereafter. It also draws much attention from birders, schoolchildren, and conservation groups. The design has since been successfully duplicated in city parks, demonstration farms, wildlife management areas, nature centers, schools, and national wildlife refuges. A kiosk may be added to any existing Chimney Swift tower by installing four corner posts and a display panel on each side. However, construction will be simplified if the kiosk is included in the initial design. These plans detail how to incorporate a roofed kiosk into the initial construction of the previously described 12 ft. freestanding tower. The list of materials is for the kiosk only. For a complete list of tower materials, refer to the previous section. It is very important to note that no part of the kiosk or roof in this design is actually connected to the tower (see Figure 8). Although this feature may appear to complicate the construction, it ensures that the nest chamber can be protected from ants.

Materials Because of its durability, pressure-treated lumber is recommended for all kiosk parts marked with an asterisk (*). 4 × 4 in. × 8 ft. lumber (posts) (4)* 2 × 6 in. × 8 ft. lumber (roof framing) (5)* 2 × 4 in. × 12 ft. lumber (fascia) (2)*

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4 × 8 ft. × ¾ in. plywood (roof decking) (2)* 30 lb. roofing felt (“tar paper”) (25 sq. ft.) asphalt shingles (or other roofing material) (25 sq. ft.) 2 × 2 in. × 10 ft. edge flashing (outside edge of roof) (2) 3 × 4 in. × 10 ft. edge flashing (inside edge of roof) (1) ¼ × 6 in. lag bolts (foundation) (8) 1⅝ in. deck screws (for attaching plywood decking to framing) (½ lb.) 3 in. deck screws (general assembly and bracing) (1 lb.) ¾ in. roofing nails (¼ lb.) 4 × 8 ft. × ⅝ in. T1-11 siding or other exterior plywood product (display panels) (2) 2 × 2 in. × 8 ft. (display panel frames) (8)*

Setting the Corner Posts Refer to “Construction of the Foundation Form” in the previous section, follow step one through step four, and then proceed as follows. Using 3 in. deck screws, secure a 4 × 4 in. post in each inside corner of the form box. Use a framing level to ensure that each post is perfectly vertical, and use temporary 2 × 4 in. braces to hold each post in place. The braces should be attached 6 in. below the tops of the posts and will remain in place until the roof of the kiosk is completed. Install two 6 in. lag bolts into the inside corner of each post so that 4 in. of each bolt extend toward the center of the form box. Place the top bolt 1 in. below the top of the form box, and place the bottom bolt 4 in. below the top bolt (see Figure 7). Continue with construction through step four as described in “Preparation and Installation of the Bottom Tower Section” in the previous section. The tower base can be easily braced to the corner

Wooden Towers

posts instead of using wooden stakes. Once these steps have been completed, install a two-layer grid of ⅜ in. rebar (spaced 10–12 in.). Using tie wire, connect each layer to the lag screws on the posts. Continue by pouring the concrete slab as described in step five and step six. The kiosk roof should be framed and decked with the ¾ in. plywood before continuing with tower construction. Once the roof is decked, it acts as a convenient scaffold for working on the upper sections of the tower. Install the roofing felt, flashing, and shingles only after the tower is completed. This will prevent damage to the final surUsing the Kiosk Tower roof as a scaffold.

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face while you stand on the roof during tower construction. Start by trimming all the 4 × 4 in. corner posts to the same height. The frame for the roof can be built one piece at a time directly onto the corner posts. However, it is easier to build the frame on the ground as a unit (see framing details in Figures 8 and 9). It can then be lifted into place on top of the trimmed corner posts where it is secured with several 3 in. deck screws. Once the plywood decking and fascia are installed, return to “Completing the Nesting Chamber” in the previous section, and proceed as directed. After the tower is completed and the predator guard is in place, install the roofing material. As soon as the tower and roof are completed, remove the temporary 2 × 4 in. braces, form box, and stakes. The corner posts and roof framing can be painted or stained at this stage of construction. Do not be concerned if the outer structure of the kiosk and roof seem unstable at this point. Once the display panels are in place, the kiosk will be completely rigid.

The Display Panels The display panels can be constructed from any desired exterior plywood or hardboard product. Each side of the kiosk will need a 2 × 2 in. frame to fit between the 4 × 4 in. corner posts. Each frame should measure 48 in. tall to make the best use of the 4 × 8 ft. material. The overall width of each frame should measure ⅛ to ¼ in. less than the actual distance between the posts to facilitate installation. Once the frames are assembled, cut the selected panel material to size, and attach it to the back of the frames with 1⅝ in. deck screws. At least one panel must be easily removable for access to the tower during routine annual tower

Wooden Towers

.

Figure 6. Kiosk Tower detail.

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Figure 7. Kiosk Tower foundation detail.

Wooden Towers

Figure 8. Kiosk Tower roof framing detail.

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Figure 9. Expanded roof detail from Figure 8.

Wooden Towers

maintenance. The panel units are most easily installed by placing screws through the 2 × 2 in. frames into the corner posts—four screws per panel are sufficient. The area between the bottom of the display panels and the foundation may be covered with hardware cloth or other wire mesh for added protection of the nest chamber. Many variations and modifications may be made to the display panels to suit each particular site. For instance, additional hinged outer frames with clear acrylic doors would protect displays and allow them to be easily changed. Brochure racks could also be installed for distributing information.

Other Wooden Tower Designs Although our best results have come from 12 ft. tall towers, we have had success with both smaller and larger structures. Some have been as large as 32 × 32 in. inside and stood more than 20 ft. tall. These have been commonly used as roosts and have routinely hosted more than one hundred swifts in late summer and during fall migration. In all cases, these larger towers have been attached to an existing structure or created as an integral part of new construction. Other successful towers have been as small as 14⅝ × 14⅝ in. × 8 ft. tall. The basic construction of the nest chamber is the same as with the 12 ft. version, but the middle section is omitted. To compensate for overheating that occurred in our original 8 ft. design, we replaced the ¾ in. spacers used in the 12 ft. towers with 1½ in. material. The ¾ in. rigid, foil-backed insulation is still installed next to the nest chamber. This creates a ¾ in. air space between the insulation and the outer wall. If vents are placed in the top and bottom edges of the final sheathing, the air heated in the space moves up and

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The house at Chaetura Canyon. This is the home where two 18 x 18 in. x 22 ft. towers were built onto the existing structure and where Chimney Swift research has been conducted over a twenty-year period.

Driftwood water barn. This structure was designed for rainwater collection. It has a Chimney Swift tower on each of four corners that measure 32 x 32 in. x 24 ft. tall.

Wooden Towers

An 8 ft. Chimney Swift tower.

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out before it can penetrate to the interior of the tower where the birds are nesting. These 8 ft. tall towers are ideal for neighborhood backyards where community restrictions may prohibit taller structures.

The Prism Tower: A Lesson in Tower Design One summer day as we were driving through Dripping Springs, Texas, our eyes were drawn to the signage for a small shopping center. Rising out of the asphalt parking lot was a three-sided plywood column supported by three steel legs. Signs for each of the tenants in the shopping center were attached to the outside of the tower. When we pulled in to investigate the structure, we noted that there was no bottom or top and that there were bird droppings on the asphalt between

A ventilated Chimney Swift tower.

Wooden Towers

An “accidental” Chimney Swift tower. the tower legs. Looking from the bottom, up into the column, we saw a Chimney Swift nest and several young swifts clinging to the inside wall. This 16 ft. “accidental” Chimney Swift tower was made by bolting two 4 × 8 ft. sheets of plywood siding to each side of a triangular welded steel frame. Inspired by this simple design, we decided to

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build a smaller version and hope for the swifts to test it. “The Prism Tower,” as we dubbed it, went through several early nest failures and design changes over five years. However, the resulting modified design proved to be one of our most successful small towers. For the legs of our version, we used three pieces of 10 ft. × 1½ in. galvanized pipe that is typically sold as line posts for chain-link fence construction. Using 1 in. sheet metal screws, we attached six 24 × 48 in. panels of ⅝ in. T1-11 with the grooves facing inward and running horizontally. This provided a nesting chamber that measured 20 × 20 in. × 8 ft., with three 2 ft. legs protruding from the bottom. Two pieces of ¾ in. treated plywood served as top and bottom for the nest chamber. The top had a 16 in. circle cut out of the center. We carried the completed tower (intact) to the corner of a fence line, secured it to the fence posts with bailing wire, and crossed our fingers. Chimney Swifts built a nest in the Prism the first year. However, direct sunlight was able to penetrate deeply enough to hit the nest, and the eggs did not hatch. The next winter, we moved the tower to a clearing with afternoon shade about 60 ft. from the original location and poured a 3 × 3 ft. × 6 in. steelreinforced slab around the legs. We made several modifications in an attempt to prevent overheating of the tower: 1. Oriented the tower with one wall facing due north. This meant that there was no wall facing due south to absorb heat from the midday sun. 2. Drilled the bottom of the tower with a grid of ⅜ in. holes to improve ventilation yet exclude snakes.

Wooden Towers

3. Removed the original top. The replacement had a smaller triangular opening measuring  in. on each side. The top was installed so that the opening was located on the northwest corner of the top of the tower. 4. Fastened ¾ ×  in. spacers around the edges of the tower and installed an outer skin of ⅛ in. white Melamine shower wallboard, creating a ¾ in. space between the nest chamber and the outer skin. Vent holes were drilled near the top and bottom of each side of the outer skin to improve air circulation. Although the next summer season was unusually hot, a pair of swifts successfully raised a nest of three young. Shortly after the first brood fledged, a second clutch of eggs was laid. Temperatures climbed even higher and exceeded 100ºF for several consecutive days when the second brood was approximately twelve days old. In spite of the improvements, the record heat was too much for the nestlings, and they all expired. Still, the fact that the first brood was successful encouraged us. The second winter after the Prism was built, additional modifications were made in an attempt to prevent overheating: 1. Placed additional ¾ × 2 in. spacers around all edges of the tower over the existing outer skin. 2. Installed ¾ in. rigid, foil-backed insulation board on all walls between the spacers, with the foil facing out. 3. Installed vinyl siding over the insulation and spacers.

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The Prism Tower. In the summer of 2000, the drought of the previous year continued with a vengeance. One day in the peak of the nesting season after the temperatures had reached 100ºF to 107ºF for twelve consecutive days, we monitored the Prism at dusk, expecting the worst. However, after only a few minutes, an adult swift entered the tower and was greeted with the unmistakable sound of healthy, hungry baby Chimney Swifts. All five of the young fledged in a year when the mercury topped 100ºF for forty-one days. That same year, some larger, but less well insulated towers in our region failed to produce adequate protection from the intense summer heat.

Masonry Towers

Masonry Towers B

ECAUSE CHIMNEY SWIFTS now commonly use chimneys rather than hollow trees as nest and roost sites, it makes sense to consider masonry construction when building new habitat for them. Brick and ceramic flue tiles are the materials used in masonry chimney construction, and they could be used to construct freestanding Chimney Swift towers. But precast cinder block is a material that is relatively easy to use and has shown some considerable promise for tower construction. There are several benefits of using cinder block as a construction material for Chimney Swift towers: cinder blocks are durable, they provide excellent insulation, the texture of the inside walls is ideal for swifts to grip with their claws, and they are freestanding. The only disadvantages of using cinder block are that the surface is not fibrous as wood is and a powdery substance often forms on the blocks. Consequently, the nest-building saliva of the swifts does not adhere as well as it does to the inside walls of wooden towers. Cinder block must be cleaned and sealed to prevent the swifts’ nests from peeling loose from the inside walls. This treatment must be repeated every year. Basic construction of all experimental designs has been the same. Using K in. joints of prebagged mortar mix, we laid hollow cinder blocks on steelreinforced concrete slabs. In larger towers, 8 × 8 × 16 in. and 8 × 8 × 8 in. blocks were used. In smaller towers, 4 × 8 × 16 in. blocks were used. We laid

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Nestlings in a cinderblock tower. three courses each day and set strips of ½ × ½ in. galvanized hardware cloth in the horizontal mortar joints every three layers.

Building a Chimney Swift Castle The Castle was built in 1994. It has been used as a nest tower as well as a summer and fall roost site every year since it was completed. The following instructions assume a basic knowledge of masonry construction techniques. There are many do-ityourself booklets on the market that can be very helpful to the novice mason. These are commonly available at most home-improvement centers. The slab is a larger version of the one described for wooden towers in a previous chapter. Materials will vary depending on the actual size of the slab.

Masonry Towers

The Castle.

Materials 8 × 8 × 16 in. hollow cinder blocks (167) 8 × 8 × 8 in. hollow cinder blocks (10) 5 ft. × ⅜ in. rebar (12) 6 × 46½ × ½ in. galvanized hardware cloth (22) mortar mix and ready-mix concrete Door: material will vary depending on size and style Roof: 48 × 48 × ¾ in. treated plywood (½ sheet)

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Start the construction by pouring a concrete slab that measures at least 5 × 5 ft. × 10 in. and is reinforced with two horizontal grids of ⅜ in. steel rebar. The tower itself measures 48 × 48 in. × 12 ft. tall on the outside and 32 × 32 in. × 12 ft. tall on the inside. Reinforce the corners by running a vertical piece of ⅜ in. rebar and filling those blocks with solid concrete. Only three or four layers, or “courses,” should be laid each day with a ⅜ in. mortar joint between each. Lay the blocks in each course in such a way that they overlap the blocks in the course below (see Figure 11). For increased strength, a 6 in. wide layer of ½ × ½ in. galvanized hardware cloth or other wire mesh can be embedded in the mortar joint every three courses, as well as between courses sixteen and seventeen (see Figure 10). In the top course, the middle block in each side can be omitted. This gives a castlelike appearance to the structure. During construction, allow

Laying cinder block for the Castle.

Masonry Towers

Stucco lining in a cinderblock tower. The stucco is first troweled on in a thick layer. Horizontal grooves are then created with a large putty knife.

the mortar to ooze from between the layers of cinder blocks on the inside of the structure. These protrusions will provide additional texture and places for the swifts to attach their nest to the wall. The outside surface of the tower should be as smooth as possible. Once the seventh course is laid and allowed to harden for twenty-four hours, an access door can then be framed into the east or north side for maintenance purposes. Fit the door with a row of 3 in. ventilation holes along the bottom, backed with ½ × ½ in. galvanized hardware cloth to exclude snakes and other small predators. Provide drainage at the bottom of the door so that the tower will not fill with rainwater, but any holes must be no larger than ⅜ in. in diameter. Install a locking latch to prevent unauthorized human access. If the tower is left open the full 32 in. all the way to the top, too much sunlight will enter the

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Masonry Towers

Chimney Swifts investigating the Castle.

structure, causing nest failure. The simplest method of reducing the top opening is to install a piece of ¾ in. treated plywood with a 16 × 16 in. hole located on the top north edge of the tower (see Figure 12). A more durable and elaborate roof can be created by installing framing and steel reinforcing and pouring a 4 in. thick concrete top. The surface of cinder block is “crumbly.” This problem can be corrected by coating the inside walls with a latex (water-based) masonry sealer. This stabilizes the surface while retaining the rough texture of the material. This coating needs to be reapplied every year. A paint roller on an extension pole works well for this process. Another alternative may be to apply a rough, heavily textured layer of stucco to the inside of the tower. Complete the construction by applying a coat of masonry cement or smooth stucco to the outer walls, creating a smooth surface that is impossible for predators to scale.

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Figure 10. Castle construction detail: front view.

Masonry Towers

Figure 11. Castle construction detail: overhead view.

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Figure 12. Castle construction detail: top section.

Masonry Towers

The Middendorf Tower.

Other Masonry Tower Designs The Middendorf Tower As a memorial to her grandmother, Lydia Middendorf built a smaller version of the Castle. It measures 16 × 16 in. inside and 32 × 32 in. outside, stands 10 ft. tall, and is set on a 4 × 4 ft. × 9 in. steel-reinforced concrete slab. As with the Castle, the corners of the hollow blocks are Wlled with concrete and have _ in. steel rebar running though the full height of the structure. There is an access door for fall maintenance on the east side with a lock and ventilation holes.

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The Pool Towers. The Pool Towers were so named because they were constructed next to a small water feature created for the local wildlife. Their experimental purpose was to test smaller versions of the successful cinder-block Castle and to test the swifts’ reaction to potential nesting sites in close proximity to one another.

Clean-out door detail.

Masonry Towers

The Pool Towers The Pool Towers are a pair of towers that measure 20 × 20 in. × 10½ ft. tall on the outside. Each course of the towers consists of four 4 × 8 × 16 in. cinder blocks. This creates an inside diameter of 12 × 12 in. The towers are set on U-shaped solid concrete bases that are fitted with ventilated clean-out doors. They both stand on a single steel-reinforced slab that measures 7 × 2 ft. × 6 in. thick. They are decorative in nature and provide an interesting visual feature in the landscape as well as habitat for nesting Chimney Swifts. One of the Fence Towers.

The Fence Towers The Fence Towers are identical in construction to the Pool Towers, but they are spaced 60 ft. apart along a fence line. A similar approach could be used in the construction of cinder-block privacy walls with the towers acting as stabilizer columns. The Lime Creek Homestead Tower Mel Rinn constructed the Lime Creek Homestead Tower from cinder blocks known as pilasters. Each block measures 16 × 16 × 8 in. tall. The walls of the blocks are 2 in. thick, leaving a 12 × 12 in. hollow center. The blocks are stacked using a ⅜ in. mortar joint. Because the walls of the blocks are only 2 in. thick, the lower section of the tower is covered with ½ in. rigid foam insulation board, a layer of hand-poured rustic bricks, and a final layer of native limestone. This provides considerable protection from overheating. Although the construction is new, the effect is that of the ruins of an early-twentieth-century homestead.

The Lime Creek Tower.

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The Limestone Tower.

The Limestone Tower Melanie Pavlas and her family constructed the Limestone Tower of 8 in. thick quarried native rock. The tower’s outside measurements are 29 × 30 in. × 10 ft. tall. The top opening is reduced to 12 in. Chimney Swifts adopted it the first year it was in place, and it is a fine use of natural materials.

Masonry Towers

The Muleshoe Bend Tower.

The Muleshoe Bend Tower The Lower Colorado River Authority (LCRA) built the Muleshoe Bend Tower in Central Texas at the entrance to a park. The LCRA designed and constructed this 12 ft. tall column of natural rock. The native stone feature was built to hold a lighting fixture but surrounds a 16 in., hollow cinderblock center for the benefit of Chimney Swifts. This is an excellent example of integrating Chimney Swift habitat into an architectural feature.

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A Conservation Plan Using Multiple Towers C

HIMNEY SWIFTS are very social birds except when nesting is involved. A large tower may attract multitudes of swifts, but there will only be one active nest per structure per year. For multiple nests, multiple towers are required. Our research indicates that nest sites should be at least 10 ft. apart. A good conservation plan for the use of multiple towers is to follow the evolution of Chaetura Canyon, where much of the research on tower design has taken place. We began with two large towers to accommodate two nesting pairs and a roost or migratory flock. A single large tower would also be suffcient. Once the original towers were adopted by swifts, smaller “satellite” towers were added as space and time allowed. Chimney Swifts typically return to a successful nest site year after year with the same mate— and so do their offspring. The year-old birds will seek out nesting sites of their own, and their search begins in the familiar area of their nursery tower. Newly constructed towers in the area are usually appropriated the first spring after they are erected. Where there are multiple towers, the full range of aerial acrobatics can be observed as the swifts interact with each other. Individuals will tumble from above and stall over a neighbor’s tower for a glimpse of the nest, eggs, and young within; play-

Conservation Plan

ful chases and kiting behavior may be seen as well as the trademark courtship “V,” with wings held up by gliding mated pairs. When the young swifts fledge, the real fun begins as they explore the world outside their nursery towers. Soon there will be “tagging” of both inanimate objects and startled perching songbirds. And of course, there is the cheerful chippering and chattering that is so commonly associated with frolicking Chimney Swifts.

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Monitoring Roost and Nest Sites W

E OFTEN SAY that observing Chimney Swifts is “a pain in the neck.” This is literally true because most of their activity takes place high above treetop level. One must be constantly looking up to observe swifts’ “kiting,” “V-ing,” “cracking-thewhip,” “parading,” and feeding maneuvers. If observing Chimney Swifts in the open sky is difficult, directly observing them in the nest or roost site is nearly impossible. Even if direct access is possible, too much interference (or any interference at the wrong time) may cause the swifts to abandon the site. This is certainly the case if the swifts’ activities are disrupted during their site selection or nest-building activities. Frightening an incubating bird from the nest may cause eggs to be destroyed when accidentally knocked over the edge. Any intrusion into a nesting chamber containing young swifts can cause startled nestlings to fall to the bottom of the site, resulting in injury. If older nestlings are prematurely flushed from the site, they will not survive. Fortunately, there are several ways to know what is transpiring in a chimney or tower without ever looking inside while the swifts are in residence. Actually seeing a single Chimney Swift enter a site during the day is a chance event at best, especially early in the season. The best time and place

Monitoring Roost and Nest Sites

to observe swifts around their home is at dusk and from a distance. If swifts are suspected or known to occupy a structure, patiently and quietly observe from at least thirty feet away. Begin observing approximately thirty minutes before sunset. Most weather forecasts include time of sunset in their daily report. Pair bonding begins soon after the return of the swifts to their breeding area from their South American wintering grounds, so groups of two to five or more birds will fly in tight formation, uttering their staccato, chippering vocalizations. A mated pair will reveal themselves when they both snap their wings up into a stationary “V” position and glide one behind the other. Swifts will generally make several passes and circle the structure before entering. Many birds have unique postures when tumbling from the sky, which can be very entertaining for the observer. Roosting structures may contain as few as a dozen or as many as several thousand Chimney Swifts. Generally, roosting birds arrive in “waves.” The first arrivals will circle the area, foraging and vocalizing before entering. Additional birds will continue to arrive, circle, and enter the structure as dusk falls. Observers who are interested in counting swifts should monitor the sky until dark, counting individual birds as they enter the site. We have found that a hand-held athletic lap counter works well for counting individuals in roosts of up to two hundred birds. Larger roosts require some estimating. An effective method is to count birds in fives or tens as they enter a site. A lap counter can still be effective. The number indicated on the counter can be multiplied for a reasonably accurate estimate. Chimney Swift vocalizations also offer aid in determining the activity in and around a structure.

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Inside a nesting structure, mated birds will utter soft chippering calls. Occasionally, the sound of their wings as they fly up and down the interior can be heard from outside. Very excited and loud chippering accompanied by a clapping sound as the swifts snap their wings usually denotes aggression or a territorial dispute. Nestling swifts produce at least two different calls, which usually become audible from outside the structure after the birds reach ten days of age. The raucous chatter they produce each time an adult enters indicates that the young are being fed. A mechanical, rasping call indicates fear or agitation. Hearing either call indicates an active nest. These sounds will cease after the young have fledged: approximately eighteen to twenty days after the sounds are first audible. After Chimney Swifts have migrated from the area in the fall, an inspection of the bottom of a nest site can be very informative. The shear volume of droppings can indicate whether the site was occupied by a few or many swifts. When dried, the average droppings produced by a family of five or six Chimney Swifts during their summer stay will fill a one-quart plastic bag. Also, Chimney Swift parents remove eggshells from the nest just as songbirds do. However, they do not carry them away. Instead, they toss the shells over the edge of the nest, and fragments collect on the bottom of the tower. A hatchling emerges from the egg by breaking completely through the shell. Half shells indicate a successful hatching. Unevenly broken segments of shell usually indicate a fallen egg. All pieces of eggshell will have a leathery appearance. Bits of material used for nesting, as well as the construction of the nest, can be examined. It is sometimes possible to identify the favorite species of tree that was used. Hardened threads of trans-

Monitoring Roost and Nest Sites

lucent saliva that hold the nest together will be clearly visible. The entire old nest can and should be removed.

Electronic Monitoring

Chimney Swifts roosting in a wooden tower. Miniature surveillance cameras make it possible to observe Chimney Swift behavior without disturbing the birds.

Today’s technology offers tools not available to Chimney Swift researchers of the past. Miniature cameras make it possible to easily observe the home life of swifts without disturbing them. Weatherproof “lipstick” cameras (so named for their shape and size) are easily connected to televisions, videocassette recorders, and computer monitors. The least expensive ones are sold by companies that specialize in retail-store security equipment. Audio/video monitoring can be espe-

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cially appropriate for towers that are installed at nature centers and other educational venues. All installation of such equipment must be completed before the swifts return in the spring. The birds are very suspicious of any changes inside their nesting chamber after they arrive and may abandon the site if alterations are made. We recommend placing a camera inside the tower in a corner directly under the protective top cover. This allows the most comprehensive observation of the swifts’ activities. All cables should be secured in a corner of the tower or run on the outside of the structure in a way that eliminates any possibility of the swifts becoming entangled in the wiring. There are many infrared-equipped cameras now on the market that allow observations in complete darkness. Unfortunately, most of these emit light that is still visible to the swifts. Using such devices will distress the birds and most likely cause them to abandon a site. For our nocturnal observations, we have used equipment that has been specially designed for our research to be invisible to Chimney Swifts. We strongly discourage the use of “off-the-shelf” infrared illumination for monitoring Chimney Swift Towers.

Monitoring Roost and Nest Sites

Year _______________

North American Chimney Swift Nest Site Research Project Site Report Form It is important to gather as much information on structures that were not used as on those that were. By comparing the characteristics of both categories of structures, we will learn which new features are important to the nesting success of Chimney Swifts. Please fill out one form per nest structure. Duplicate this form as needed. We are interested in all nesting attempts, both in structures made purposely to attract Chimney Swifts and in structures such as chimneys, silos, and natural cavities. Name ___________________________________________________________ Street address _____________________________________________________ City

__________________________ State ______ Zip code ____________

Phone ________________________ Email ____________________________

Nest Structure Characteristics: Please provide a detailed description of nesting structure (attach a photo or drawing if possible). Use feet and inches for all measurements. Inside dimensions _________________________________________________ Outside dimensions ________________________________________________ Is there an air space? ___________ How wide? ______ Insulated?_________ Height ___________________ Type of material ______________________ Color of material ______________________ Notes ____________________________________________________________ _________________________________________________________________ _________________________________________________________________

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Building Chimney Swift Towers

When was the structure erected (month/day/year)? ______ /______ / ______ Is the structure freestanding or attached to a building? ___________________ If attached, please elaborate: _________________________________________ __________________________________________________________________ Which compass direction does the wall of the structure that supports the tower face? _______________________________________________________ What were the maximum/minimum air temperatures April–August (0F)? ________ /_________

Habitat around the Structure: Is the structure in a clearing or a wooded area? _________________________ What is the distance from the nearest tree that is as high as or higher than the top of the nest structure? ____________________________________________ What percentage of an imaginary 200-foot circle around the nest structure is covered by tree canopy as high as or higher than the top of the structure? _________________________________________________________________ Use of Structure by Swifts: Did Chimney Swifts ever enter the structure? _________________________ Was the structure used as a roosting site? _____________________________ Summary of Observations: First day swifts were sighted in the area: _______ / ________ / __________ First day swifts roosted in the structure: ________ / ________ / __________ Last day swifts roosted in the structure: ________ / ________ / __________ Maximum number of swifts roosting at one time: _______________________ Date of maximum roosting flock: ______________ / ________ / __________ Number of days the structure was occupied: ___________________________ Note: Disturbance during nest building may cause Chimney Swifts to abandon the site. The following data should be collected only after the nesting season is over.

Monitoring Roost and Nest Sites

Did Chimney Swifts nest in the structure? _____________________________ Was the nest successful? ____________________________________________ Height of nest from bottom of structure: _______________________________ Height of nest from top of structure: __________________________________ Height of nest aboveground: _________________________________________ What was the nest attached to? ______________________________________ Which compass direction did the wall of the structure that had the nest attached face? _______________________________________________________ If the nest failed, what were the likely causes for that failure (predators, rain, disturbance, etc.)? __________________________________________________ _________________________________________________________________ If predators were responsible for nest failure, please identify species of predator and elaborate: __________________________________________________ _________________________________________________________________ Additional comments: _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Thank you for your participation. Please return completed forms to Paul and Georgean Kyle c/o Driftwood Wildlife Association P.O. Box 300369 Austin, TX 78703-0007

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Building Chimney Swift Towers

An adult Chimney Swift with nest and young. Courtesy Richard B. Fischer

More Information

More Information I

F YOU WOULD LIKE to learn more about Chimney Swifts, you will enjoy Paul and Georgean Kyle’s book Chimney Swifts: America’s Mysterious Birds above the Fireplace. It is a uniquely personal look at these remarkable birds following more than twenty years of intimate observations and conservation efforts. After showing you the world of the Chimney Swift through their eyes, they show you a bit of the world through the keen eyes of the swifts themselves. On their Web site at www.chimneyswifts.org, you can participate in tracking spring migration as the Chimney Swifts return from South America, learn about caring for injured and displaced swifts, report fall roosting activity during the annual Swift Night Out in September, and even watch real-time nesting activity on a Chimney Swift webcam. You can also become more involved in Chimney Swift conservation efforts by joining the Driftwood Wildlife Association as a volunteer research associate in the North American Chimney Swift Nest Site Research Project. Contact the Association online or at Driftwood Wildlife Association, P.O. Box 300369, Austin, TX 78703-0007.

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