Out of the Shadows: Black Swifts, North America's Most Mysterious Birds

Habitat: Forages in the air over various habitats, from forest to open country. Nests on damp rocky cliffs, usually behind waterfalls or in sea caves.

Behavior: Spends most waking hours in continuous flight, like other swifts, catching insects in midair. Travels singly or in small flocks.

Status: Localized and uncommon throughout its range. Total population may not exceed about 20,000 birds. Scattered distribution makes it hard to census.

Threats: Because birds often nest behind waterfalls, destruction of mountain forests or the effects of a drying climate could make some sites unsuitable by reducing stream flows. Deforestation in South America also could degrade their wintering habitat.

Outlook: With its wide range, the species is in no immediate danger, but its long-term survival could be jeopardized by climate change and habitat loss.

This story originally ran in the September-October 2012 issue as "Out of the Shadows."