Riparian and other woodlands up through lodgepole pine belt are favored breeding habitats. In winter, uses open areas near bodies of water. Requires trees and snags with cavities for nesting. Yearlong, diurnal activity. The first spring transients arrive in California in late January from Mexico and Central America.
Numbers increase through spring, but diminish in summer in southern California.
In late summer and early fall, numbers increase again as transients pass through from the north. Most migration has been completed by the end of October. Small numbers regularly winter on the coast north to central California, and in the Central Valley. Incubation 13-16 days. As with other swallows, adults are swift fliers and infrequently fall prey to hawks.