On the ground, a nest may be a shallow depression lined with a few feathers and a rim of soil built up 4 to 10 inches above ground, or it may be a large mound of soil and debris with a cavity in the top. A tree-top nest is built of reeds, grass, and straw heaped on a mound of sticks interwoven with the supporting tree branches. Two or three chalky white eggs hatch in approximately 1 month. They soon develop a soft, silky down, followed by feathers. Average age at first flight is 75 days.
Brown pelicans have few natural enemies.
Although ground nests are sometimes destroyed by hurricanes, flooding, or other natural disasters, the biggest threat to pelican survival comes from man. In the late 19th and early 20th centuries, pelicans were hunted for their feathers, which adorned women's clothing, particularly hats. During the food shortages following World War I, fishermen claimed pelicans were decimating the commercial fishery resource and slaughtered them by the thousands. The nests were also frequently raided for eggs. With the advent and widespread use of pesticides such as DDT in the 1940s, pelican populations plummeted due to lack of breeding success.