Hornbills | Bucerotidae

Neushoornvogels | Cálaos

Medium-sized to very large birds with a long, downcurved bill topped in many species by a horny structure, the casque, which ranges from a low keel to a hollow crest and is kept light by internal air spaces. The head is narrow, so that the bird can see its own bill tip; the first two neck vertebrae are fused and the neck muscles and collarbones are reinforced to carry the weight of the bill, and the eyelids bear long, stiff lashes. The bill tip works as a pair of forceps: food is held between the mandibles, tossed into the air with a short jerk of the head and so delivered to the throat, the tongue being too short to work it back. In the tree-dwelling species the female walls herself into a cavity with a mixture of mud, droppings and fruit pulp until only a narrow vertical slit remains, through which the male feeds her and later the young; she stays there for weeks to months and in some genera moults flight and tail feathers all at once during that time. The ground hornbills depart from this: they do not seal the nest, forage on foot on the ground and breed in groups with helpers. The flight is heavy and in the larger species loudly whooshing, because the wing coverts do not fully close over the upper arm and the air beats through between the flight feathers.