Sooty, dusky birds seen on the wing, never resting except in chimneys of
houses, or hollow trees, where they nest. Tips of tail feathers with sharp
spines, used as props. They show their kinship with the goatsuckers in their
nocturnal as well as diurnal habits, their small bills and large mouths for
catching insects on the wing, and their weak feet. Gregarious, especially at
the nesting season.
Chimney Swift.