Colonies often contain other species of birds. Reproduction Mating behavior includes a variety of threats and snapping displays plus preening, raising the feathers of the crown, breast, throat, and back, and fully erecting the head plumes. Clutches are three to six sea-green eggs, laid at intervals of two days. Both parents take turns incubating the eggs, which takes 21-26 days. They frequently raise two broods a year, and two sets of young birds may share the nest.
Birds sometimes breed in their second year, before they attain adult plumage.
Diet Fish, frogs, insects, tadpoles, young birds, small mammals, snakes, salamanders, mollusks, crustaceans, marine animals, and vegetable matter such as algae. Men are their worst enemies. Much of their habitat is being lost, and because the birds often raid fish hatcheries, they are sometimes considered pests and killed. In Japan, they are important in history and folklore. They nest locally at Utah's Bear River National Wildlife refuge, where they are commonly seen in the spring and summer.