About Chaetura vauxi (J.K.Townsend, 1839)
Vaux's swift (scientific name: Chaetura vauxi (J.K.Townsend, 1839)) is a small swift, even when compared to other species in the Chaetura genus. It measures 10.7 to 11.2 cm (4.2 to 4.4 in) in length and weighs around 18 g (0.63 oz). Northern populations are slightly larger, reaching 11.5 cm (4.5 in) in length, a difference thought to follow Bergmann's Rule and/or relate to migration requirements. This species has a cigar-shaped body, crescent-shaped wings, and a short, bluntly squared-off tail. Its head, upperparts, and wings are dusky black, while its underparts, rump, and tail coverts are greyish brown. Its throat is paler grey, turning whitish in northern individuals. Males and females have similar appearances, but juveniles have dusky bases on their throat feathers. Vaux's swift breeds in highland regions ranging from southern Alaska to central California, and from southern Mexico and the northern Yucatán Peninsula to eastern Panama and northern Venezuela. Populations residing in the United States are migratory, and winter from central Mexico south through the species' Central American breeding range. Resident breeding birds found in the southern part of the overall range are sometimes classified as a separate species: the dusky-backed swift, Chaetura richmondi. This species' preferred habitat is old growth coniferous or deciduous forests, and it requires large, hollow trees for nesting.
