The Chimney Swift is one of about 80 species worldwide and four that regularly occur in North America (Terres 1982). It is the most common swift in the eastern half of the continent, and one of only two species of breeding swifts in Texas (Oberholser 1974).
DISTRIBUTION: In 1925, Chimney Swifts were seldom seen in central Texas. By 1940 they were relatively common in Austin. Oberholser notes that in the 1950s and 1960s their breeding range had spread west and south but was still confined to the eastern two-thirds of Texas. With some additional frequency in western-most portions of its range, TBBAP data corroborate Oberholser’s observations of the bird.
Both the extension and limit of the range are directly related to human activity. Adapting to the historically new habitat of chimneys, air shafts and other structures instead of hollow trees, the Chimney Swift followed development westward across North America and Texas. The paucity of habitat (natural and man-made) in the Trans-Pecos region acts as a barrier to further expansion. Including the TBBAP data, only three possible records exist for the Trans-Pecos region (Wauer 1973, Oberholser 1974).
SEASONAL OCCURRENCE: Although the presence of Chimney Swifts is easy to establish by their vocal “chippering” and aerial displays, breeding is more difficult to confirm. Of the 941 records obtained by the TBBAP, only 19% were confirmed. Because of the inaccessibility of most nest sites (usually deep, narrow shafts), only 36 of these confirmations resulted from the discovery of active nests with eggs or young. The presence of non-breeding spring and summer roosting flocks further complicates confirmation (Kyle and Kyle 1994).
The breeding season for Chimney Swifts in Texas begins in late April (eggs) and continues into August (young on or around the nest). Oberholser notes that the early and late dates for eggs are May 5 and July 5, respectively. The TBBAP data document a nest with young on 10 May 1987 at latilong 30099, quad A1. Given an incubation period of 19 to 21 days (Sherman 1952, Fischer 1958), this indicates an early egg date of no later than 21 April 1987. A fallen nest with young aged two to six days was taken to licensed rehabilitators on 8 August 1992 in latilong 30097, quad C6 (Texas Parks and Wildlife Department Annual Species Report). This indicates a late date for eggs no earlier than 28 July 1992.
BREEDING HABITAT: Formerly nesting in hollow trees, the Chimney Swift now nests almost exclusively in man-made structures. The bird’s necessity to cling to textured vertical surfaces when not in flight limits roost and nest sites to dark, hollow shafts such as masonry chimneys or airshafts of wood or brick.
Other less common nest sites include wells (Oberholser 1974), a fiberglass cistern and masonry bar-b-que pit (D. Connell, pers. comm.) and the interior of a log out-building (J. Parker, pers. comm.). Essentially Chimney Swifts will readily accept hollow structures of wood or masonry that are 1.83 m (6 ft.) or more in depth, closed on all sides and relatively dark.
The semi-circular nest is attached with the swifts’ glue-like saliva to a vertical surface usually in the bottom 1/3 of the shaft. It is constructed of small twigs, pine or juniper needles, has a basket-like appearance and is unlined. A nest may be reused in the same reeding season if an early brood is lost. Reuse of an existing nest in subsequent breeding seasons is rare, but not undocumented in Texas (Kyle and Kyle 1994) and elsewhere (Dexter 1978). Normally a new nest is constructed each year. Chimney Swifts are considered to be single brooded. However, in June 1995 at latilong 30097, quad D8 a pair began incubating a second clutch before their first brood had dispersed (Kyle and Kyle 1995).
Multiple nests in a shaft are from previous seasons and do not indicate communal nesting. Chimney Swifts are solitary nesters. A pair may allow several “helpers” to join them (Dexter 1952), but only one nest per site will be active at any one time. In some cases, a roost of non-breeding birds may coexist with the breeding pair. The roosting birds occupy the upper section of the tower — well away from the active nest (Kyle and Kyle 1994).
STATUS: The status of the Chimney Swift in Texas (and throughout its breeding range) is deteriorating. The range as determined by TBBAP records was slightly increased over the area described by Oberholser in 1974. However, more recent data show an overall decline throughout North America. In Texas, the trend for 1966 – 1994 was a 1.5% decline.
Even more disturbing was a decline of 2.5 % from 1980 – 1994 (Sauer, et. al. 1996).
The increase in the range of the Chimney Swift during the middle of this century was a direct result of human activity. This is also true of the recent decline in numbers. Although the activity is illegal, professional chimney-cleaning companies commonly remove active nests, destroy the eggs, and kill the young at the request of clients. This disturbingly common activity directly decreases the productivity of the birds. The capping of chimneys to exclude Chimney Swifts has significantly decreased the number of suitable nest sites. Many traditional roost and nest sites are in old and dilapidated structures that are demolished for new construction. Chimneys are not as common as they once were, and new chimney construction is most commonly stainless steel. These are unsuitable because they are too slick to accommodate the swifts and their nests.
Chimney Swifts will readily accept a variety of sizes and designs of artificial chimneys and towers as nest and roost sites (Sherman 1952, Kyle and Kyle 1996). The recovery of Eastern Bluebirds and Purple Martins has been aided by providing additional habitat, conserving existing habitat and educating the public. It may be possible to reverse the declining trend in Chimney Swifts by using a similar strategy.
Text by Paul D. and Georgean Z. Kyle (ca. 1997)
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