Large seabird of inshore waters, often seen from beaches off the Pacific coast, sometimes just beyond the breakers. Usually plunge-dives from a shallow angle, much closer to the water than the Blue-footed Booby. Breeds in colonies on offshore islands, nesting on the ground. Head, neck, and upperparts are solidly brown, except for adult males from Pacific coast populations which have a whitish head and often an entirely whitish neck. Adult has well-demarcated white belly and immature has a variably mottled brown belly that rarely looks solidly brown below.