hornbill, common name for members of the family Bucerotidae, Old World birds of tropical and subtropical forests, named for their enormous down-curved bills surmounted by grotesque horny casques. From 2 to 5 ft (61-152.5 cm) in length, they are the largest of an order that also includes the kingfishers. Hornbills are black and dark brown with patches of white or cream on the body, wings, and tail. The bill is usually brownish, though in some species it is black, red, or yellow. Omnivorous, hornbills eat fruits, berries, insects, and small animals. They have loud, far-carrying voices and a variety of calls, including brays, toots, bellows, and cackles. They are noted for their unusual nesting habits; presumably as a defense against monkeys and snakes, the female is sealed into the nesting cavity by the male, who feeds her through a bill-sized aperture for a period of from 6 weeks to 3 months while she incubates the eggs. This practice, and the fact that hornbills mate for life, has made them the subject of superstition among native tribes, who use them (or representations of them) in religious rituals as symbols of purity and fidelity. The great hornbill, Buceros bicornis, ranges from India to Indochina and Sumatra. Hornbills are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Coraciiformes, family Bucerotidae.

Any of about 45 species of Old World tropical birds (family Bucerotidae) noted for the bony helmet on the bill of some species. Hornbills range from 16 to 63 in. (40–160 cm) long, and typically have a large head, prominent bill, thin neck, broad wings, long tail, and brown or black plumage, usually with bold white markings. They nest in cavities, usually in large trees. The male of most species walls up the female in the nest, closing the hole with mud, except for a small opening through which he passes food. The female breaks out after the eggs hatch, but the young may be walled up again.

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