The hornbills (Bucerotidae) are a family of bird found in tropical and subtropicalAfrica, Asia and Melanesia. They are characterized by a long, down-curved bill which is frequently brightly colored and sometimes has a casque on the upper mandible. Both the common Englishand the scientific name of the family refer to the shape of the bill, "buceros" being "cow horn" in Greek. Hornbs have a two-lobed kidney. They are the only birds in which the first and second neck vertebrae (the atlas and axis respectively) 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.