The high-flying Black Swift is the largest swift found in the United States, at over seven inches long. It is black overall with a pale gray head, and appears very long-winged while in flight. Like other swifts, it spends most of its life on the wing, where it feeds exclusively on flying insects. Its feet are tiny and weak, so this bird does not perch, but clings to the vertical cliff walls where it nests.
A recent study conducted by the Rocky Mountain Bird Observatory has revealed that at least some Black Swifts migrate about 4,300 miles to winter in lowland rainforest in western Brazil.
Black Swifts usually lay a single egg in a shallow nest made of moss bound with mud, usually close to or behind waterfalls. Clutches consist of a single egg. This species has one of the most prolonged nestling periods of North American birds, beginning nesting in June, with young birds leaving the nest in September, immediately before migration begins. Adult birds often leave their young for the entire day, returning to feed them near dusk; the young birds spend the day in a state of torpor, or “suspended animation” awaiting their return.
Threats to this species include pesticide use, which may cause a decrease in the swift’s insect food. Nesting sites need protection from disturbance by hikers and rock climbers during the breeding season, particularly on public lands. More surveys are needed to identify nesting sites across the range of the species. Climate change has led to a loss of glaciers, reducing water flow in waterfalls, one of the Black Swift’s favored nesting locales.
Read more on about this groundbreaking study.