Double-crested Cormorants nest in colonies on the ground on islands or in trees on the mainland. Most nests are built flat on the ground or amid rocks, and are made of sticks and weeds and lined with leafy twigs, grass and feathers. However, about 30 percent of Cormorants will nest in trees, where their platform nests are built of sticks and rubbish. Accumulated droppings below these nests can kill the trees—when this happens, the birds may move to a new area or simply shift to nesting on the ground.
Cormorants usually lay three or four bluish white eggs that have a chalky surface. Both adults incubate the eggs for 24-27 days, and the young fledge about 42 days after hatching. more illustrations >>