High on the western canyon cliffs these monotoned birds keep down the insect population. After nidification they gather in sizable flocks and often are seen over towns, angling and darting like miniature Nighthawks.
A. G. Vrooman of Santa Cruz, California, found the first eggs of this species in careless nests of earth, grass and rootlets on ground. Only a single egg, three times the bulk of a Chimney Swift's, is laid. They were located in undercut niches of sea cliffs by frightening the birds off with tin pans. The site, dark bird, single egg and surroundings conveyed the impression that Petrels — not Swifts — were the quarry.
Western North America from southern British Columbia and southern Colorado, south.