Hornbills are birds found in tropical and subtropical Africa, Asia and Melanesia of the family Bucerotidae. They are characterized by a long, down-curved bill which is frequently brightly coloured and sometimes has a horny casque on the upper mandible. Hornbills have a two-lobed kidney. They are the only birds in which the first and second neck vertebrae are fused together; this probably provides a more stable platform for carrying the bill. The family is omnivorous, feeding on fruit and small animals. They are monogamous breeders nesting in natural cavities in trees and sometimes cliffs. A number of mainly insular species of hornbill with small ranges are threatened with extinction, namely in Southeast Asia.
Hornbill
The brightest colours on most hornbills, like this pair of knobbed hornbills, are found on the beaks and bare skin of the face and throat.
Close-up of great hornbill
Close-up of head of a Malabar grey hornbill showing eyelashes
A casque is an anatomical feature found in some species of birds, reptiles, and amphibians. In birds, it is an enlargement of the bones of the upper mandible or the skull, either on the front of the face, or the top of the head, or both. The casque has been hypothesized to serve as a visual cue to a bird's sex, state of maturity, or social status; as reinforcement to the beak's structure; or as a resonance chamber, enhancing calls. In addition, they may be used in combat with other members of the same species, in the gathering of food, or in thermoregulation.
Like most hornbills, this male great hornbill has a distinctive casque on its upper mandible.
The bony, vascularized casque of the southern cassowary helps the bird to shed excess heat.
The high casque of the veiled chameleon provides an expanded area for the attachment of jaw musculature – and may also help the animal to collect moisture or store fat.
