hammerhead, common name for a heavy-looking, heronlike bird, Scopus umbretta. Its plumage is brown with light and dark glossy, purplish streaks on the wings and body. It has short legs, partially webbed feet, and a heavy, wide, moderately long, black bill. Its stiff, backward-pointing crest, along with its peculiar bill, give its head a hammer-shaped appearance. Both sexes are similarly arrayed. Long-winged and long-tailed, the hammerhead, or hammerkop (as it is called in Africa), may reach a body length of 20 in. (51 cm). It is an inhabitant of the marshes and mangrove swamps of southern Arabia, Africa, and Madagascar, where it feeds primarily on aquatic animals, such as water insects, small fish, and amphibians. It often perches on the back of hippopotamuses, searching for frogs. Hammerheads reside singly, in pairs, or in small flocks, near water and seldom far from trees, in the forks of which they build intricate domed nests, some 3 to 6 ft (91.5–183 cm) or more in diameter. The nests, to which the birds return each year, are complex, three-compartmented structures, lined with mud and dung, and ornamented outside with bright-colored objects. The female lays a clutch of three to six white eggs. Both sexes care for the highly dependent young. According to native superstitions, hammerheads are evil omens, and it is considered bad luck to harm them. Such superstitions have kept the birds somewhat protected. Hammerheads are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Ciconiiformes, family Scopidae.