P. occidentalis is a social species, gregarious throughout the year with colonial breeding behavior (Harrison 1996). Breeding dates vary with location, but most populations reproduce from March to August. At the Pelican Island National Wildlife Refuge in the IRL, breeding continues nearly year-round (Terres 1980).During the breeding season, nests in trees and bushes are constructed from straw or grass placed on mounds of sticks woven onto a supporting branch (Terres 1980). Ground nests are comprised of feather-lined impressions protected with a 10-25 cm rim of soil and debris. Pelicans usually lay 2-3 eggs at a time, incubating them for a period of 28-30 days (Terres 1980). Chicks in ground nests venture out by walking after approximately 35 days, while those in trees wait for about 65-80 days to fly from the nest.Hybrids of brown and white pelicans are possible, and one such offspring was on display at the National Zoo in Washington, D.C. in 1937 (Terres 1980).Voice: Adult brown pelicans are silent, rarely emitting a low croak, while hatchlings frequently squeal (e.g. Peterson 1980).