Black Swift occurs widely throughout western North America in summer, with its breeding range extending as far north as southeastern Alaska, as far east as central Colorado, and south through Mexico and Central America to Costa Rica, with additional populations in the West Indies. Despite this extensive distribution, less than 200 specific nesting localities have been documented and some of these sites are only intermittently occupied or have not been occupied in more recent years. Most nesting sites are associated with sheer cliffs and waterfalls. Nowhere in this range is it considered to be an abundant summer resident. The South American wintering range of Black Swift populations breeding in North America only recently was determined. The winter range of Central American and a portion of the West Indian breeding populations have yet to be defined, although these probably also are in South America. There are several unique aspects of the breeding biology of the Black Swift: clutch size consists of a single egg, incubation and fledging periods are long, and the species forages exclusively on aerial plankton.