- 4.3 in
- 11 in
- 0.5–0.8 oz
- Martinet de Vaux (French)
- Vencejo de Vaux (Spanish)
- Vaux's Swift is the smallest swift in North America.
- Vaux's Swifts roost communally, by the hundreds or sometimes the thousands, presumably to conserve heat. They let their body temperature drop and become torpid on cold nights, reviving in the warmth of day.
- Vaux's Swifts descend into their roost tree essentially at once, spiraling down in a very dramatic rush at nightfall.
- Vaux's Swift is named for William S. Vaux, a member of the Academy of Natural Sciences and a friend of John K. Townsend, who first described the species. The name is pronounced "vawks," not "voh."
- The oldest recorded Vaux's Swift was at least 5 years, 1 month old when it was recaptured and rereleased during banding operations in Venezuela.
Nests in coniferous or mixed forest. Forages in forest openings, especially above streams.
Flying insects and some spiders.
- Clutch Size
- 3–7 eggs
- Egg Description
- Condition at Hatching
- Naked and helpless.
Half-cup made of small twigs glued to vertical surface with the bird's sticky saliva. Nests communally, usually in hollow trees, less commonly in chimneys.
Forages in the air, taking insects in its bill.
Vaux's Swift declined across most of its range by almost 2% per year between 1966 and 2014, resulting in a cumulative decline of 57%, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 600,000, with 41% spending some part of the year in the U.S., 52% in Mexico, and 14% breeding in Canada. The species rates an 11 out of 20 on the Continental Concern Score. Vaux's Swift is not on the 2014 State of the Birds Watch List. Logging of large-diameter trees in old-growth forests eliminates nest sites.