Chimney Swift Towers: New Habitat for America's Mysterious Birds

Tower Construction Basics

Tower Construction Basics 19 Tower Construction Basics WHEN 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 Chimney Swift Towers 20 A typical Chimney Swift tower. 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 Tower Construction Basics 21 Chimney Swift Towers 22 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...