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Status: Population size: 410,000

White-throated Swift
(Aeronautes saxatalis)

This species was on the 2002 WatchList, but is not on the 2007 WatchList. Please refer to http://web1.audubon.org/science/species/watchlist/techReport.php for information on the 2007 WatchList.

A still relatively common inhabitant of the western part of the U.S. where its traditional nesting and roosting places have been openings in bluffs and canyons and cliffs, the White-throated Swift has proven to be extremely adaptable and now will seek out crevices in bridge trusses, highway overpasses, buildings, quarries and other manifestations of human activity. Despite this adaptability the species has shown a significant long-term decline across its U.S. and Canadian breeding range.

Identification
This swift is the only one in North America with a black-and-white pattern. Its size is intermediate between the Black Swift and the Vaux's Swift with a tail that is somewhat longer tail than other swifts and shallowly notched. Plumage is brown to black with white chin, breast and flanks. Juveniles are paler overall. The sexes are indistinguishable. This swift coexists with the Violet-green Swallow, but the latter is somewhat smaller with shorter wings, and a back that is glossy violet-green (although fresh-plumaged White-throated Swifts have a darkish-green sheen). The species has been described as a "little torpedo", as it speeds along hunting for insects and then suddenly changes directions in a spectacular display of aerial acrobatics. Like all swifts, this bird spends most of its time in foraging flight, often in flocks, and rarely resting except at the roost.

Distribution and Population Trends
In the United States, this swift breeds in eastern Washington state and eastern Oregon, and in California from Humboldt County to the Coast Ranges, the Cascades and foothills of the Sierra Nevada and the Channel Islands except Santa Barbara and San Miguel, northern Idaho, parts of Montana, through Wyoming, Utah and Nevada and along the Colorado River in California and Arizona. It breeds as far east as western South Dakota, extreme western Nebraska, central and western Colorado, and in the mountains of west Texas. It also breeds in southern British Columbia and south of the U.S., its breeding range extends from Mexico south to the interior mountains of Guatemala, El Salvador, and Honduras.

In the U.S., it winters in parts of its breeding range but retracts from northern portions and higher elevations. Regularly occurs in winter from central coastal and central inland California to southern Nevada and south to the Mexican border, including southwest Arizona. South of the U.S., it is a permanent resident within its Mexican and Central American range.

It appears that breeding ranges have expanded in coastal and central California and into British Columbia, probably because of the increasing abundance of artificial structures. However, Breeding Bird Survey trend analysis has shown a significant 2.7% per year rangewide decline from 1966-2001.

Ecology
Northward migration of migrant northern populations begins in April. Nests in crevices, fissures, or rocky shelves along coastal cliffs, bluffs, and canyons and, since the 1950's, in human-made structures.

The nest is shallow, about 10 cm in diameter and fashioned from grass, moss, feathers and other suitable material, all held together with saliva. There are usually 4-5 eggs in a clutch, non-glossy and white to cream, laid in a period of 4-6 days, followed by an incubation period of about 24 days. Depending on location, the nestling period can extend from April to August, with a peak in midsummer.

Adults exposed to prolonged cold, wet conditions may die. However, when temperatures drop and food intake has been low, swifts become hypothermic which may enable them to survive until conditions improve.

Data on the life history of this species is scarce, in part because of the difficulty of reaching and observing nests. Consequently, little is known about breeding behavior, nesting, parental care, hatching success, development and survival of newly hatched, immatures and fledglings, and dispersal from the nest. In addition, life span and survivorship are either poorly understood or have not been studied.

Threats
The general relative inaccessibility of nest sites suggests that threats at nesting sites are not a major problem though increasing numbers of recreational rock-climbers in some areas may disturb birds. A more likely broad-scale threat is from decreases in aerial insect abundance from habitat loss and use of pesticides. Birds may also be ingesting pesticides directly and bioaccumulating them in tissues which may cause decreases in reproductive output and increases in adult mortality, especially under extreme weather conditions.

Conservation
While little conservation activity has been directed at the White-throated Swift, some actions for other species may benefit this one. For example, seasonal closures of cliff areas from recreational rock-climbers to protect Peregrine Falcons and Prairie Falcons would decrease human activity near potential White-throated Swift nest sites. On public lands, government agencies should consider similar seasonal closures at known White-throated Swift nesting sites. Land protection activities in swift foraging areas should help to protect the insect populations necessary for this species survival.

Unfortunately, the lack of basic knowledge about the species' life history and factors causing population declines currently hampers our ability to take actions that we know will stop the declines and increase swift populations. Research to better understand these issues should be a priority for government and university scientists.

What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of White-throated Swifts as well as other species. To learn more about the Important Bird Area programs in states with breeding populations of White-throated Swift, and how you can help, visit: http://www.audubon.org/bird/iba/

Support local land trusts, government agencies, and other organizations working to preserve White-throated Swift foraging habitat in your area. Contact your state Important Bird Areas coordinator (http://www.audubon.org/bird/iba/state_coords.html) to find out if there are sites in your area important for White-throated Swifts that need increased protection.

Follow Audubon At Home guidelines to decrease home pesticide use for a healthy yard and neighborhood and to encourage habitat management that is beneficial to White-throated Swifts and other species. See http://www.audubon.org/bird/at_home/index.html for more information.

Volunteers are crucial to the success of programs that monitor the long-term status of wintering populations of White-throated Swift and other bird species. Audubon's Christmas Bird Count (CBC) is one of the longest-running citizen-science monitoring programs in the world and has helped to follow changes in the numbers and distribution of White-throated Swift. To learn more about the CBC and how you can participate, visit: http://www.audubon.org/bird/cbc

Information on where White-throated Swifts occur and in what numbers is vital to conserving the species. Help in monitoring this and other species by reporting your sightings to eBird. A project of Audubon and the Cornell Lab of Ornithology, eBird is the world's first comprehensive on-line bird monitoring program: http://www.audubon.org/bird/ebird/index.html.

References
Chantler, P.1995. Swifts: A Guide to the Swifts and Treeswifts of the World. Yale University Press, New Haven, CT.

Kaufman, K. 1996. Lives of North American Birds. Houghton Mifflin Company, Boston, MA.

Ryan, T. P. and C. T. Collins. 2000. White-Throated Swift (Aeronautes saxalis). In The Birds of North America, No. 526 (A. Poole and F. Gill, eds.). Ithaca: Cornell Laboratory of Ornithology; Philadelphia: The Academy of Natural Sciences; Washington, DC: The American Ornithologists' Union.