Cormorants inhabit seacoasts, lakes, and some rivers. The nest may be made of seaweed and guano on a cliff or of sticks in a bush or tree. The two to four chalky eggs, pale blue when fresh, hatch in three to five weeks, and the young mature in the third year.

Cormorants have a long hook-tipped bill, patches of bare skin on the face, and a small gular sac (throat pouch). The largest and most widespread species is the common, or great, cormorant, Phalacrocorax carbo; white-cheeked, and up to 100 cm (40 inches) long, it breeds from eastern Canada to Iceland, across Eurasia to Australia and New Zealand, and in parts of Africa. It and the slightly smaller Japanese cormorant, P. capillatus, are the species trained for fishing. The most important guano producers are the Peruvian cormorant, or guanay, P. bougainvillii, and the Cape cormorant, P. capensis, of coastal southern Africa.