White-throated Swift

The White-throated Swift, Aeronautes saxatalis, is a medium-sized bird with a striking black and white plumage. Its back and wings are a deep blackish-brown, while the underparts, including the breast, belly, chin, and throat, are a crisp white. Adults may exhibit a subtle greenish sheen on their dark feathers, though this is seldom seen in the field. Both sexes are indistinguishable by their plumage, and juveniles resemble adults but with duller head and neck feathers.

Identification Tips

Adult White-throated Swifts measure 15–18 centimeters in length and have a wingspan of approximately 35.5 cm. They possess a tail with a shallow notch, about 10 millimeters deep. Weighing between 28 and 36 grams, there is no size difference between males and females. These swifts can be differentiated from similar species, such as the American Black Swift and Vaux's Swift, by their white underparts, which the others lack.

Habitat

White-throated Swifts are often found in open areas near cliffs, rock faces, or man-made structures, where they roost. They form colonies in cliff crevices, typically 6–50 meters above the ground, and may also roost and nest among swallow colonies. Foraging occurs over meadows, agricultural fields, and open areas along ridges and hills.

Distribution

These swifts are year-round residents along the coastal and southern regions of California, Arizona, New Mexico, Texas, central Mexico, and the Sierra Madre mountains. Migratory populations breed from Arizona and New Mexico to southern British Columbia, and from central California to eastern Colorado and Wyoming. Wintering populations are found in southwestern California, eastern Arizona, the Texas Panhandle, El Salvador, Guatemala, Honduras, and Chiapas, Mexico.

Behaviour

White-throated Swifts are known for their rapid flight, rarely landing except to roost. They fly at altitudes of 10–100 meters, utilizing wind currents and updrafts. They leave their roosts in the morning and forage all day until late afternoon or evening. These swifts occasionally bathe in flight by skimming water surfaces and engage in aerial disputes with conspecifics or other bird species.

Song & Calls

Their vocalizations include a "staccato chattering" while in the air, sharp one- or two-note calls, and a shrill "scree." At roosts, they may produce "twittering" sounds, and juveniles emit higher-pitched begging calls.

Breeding

Courtship involves gliding displays and plummeting falls, leading to monogamous pair formation. Nests are constructed with plant material and feathers bound by saliva on cliffs or structures. Clutches of 4–5 white matte eggs are laid, with incubation starting after the last egg is laid. Both parents feed the nestlings, which fledge at a significantly higher weight than at hatching.

Diet and Feeding

As aerial insectivores, White-throated Swifts forage in rising air currents to capture insects such as beetles, flies, bees, and true bugs. They follow harvesting machinery to catch disturbed insects and carry arthropod boluses to feed their young. They obtain most of their water from their diet but may also drink from water bodies.

Conservation status

The White-throated Swift has experienced a decline of 2.8% from 1966–1998, potentially due to habitat loss and reduced food supply from pesticide use. While some populations are increasing and most appear stable, the overall decline is concerning, especially given the declines of other aerial insectivores.