The hornbills (Bucerotidae) are named because the shape of their bill reminded early people of cattle horns. The family has a long, down-curved bill which is frequently brightly coloured. Their beaks are often topped by a large hollow chamber called a casque. Made of keratin, casques are thought to serve as a resonating chamber to amplify the harsh braying calls. Hornbill ivory is not a true ivory as it is not a dentine material, but rather a keratin. Hornbills are the only birds known with their first two cervical vertebrae fused, which most likely helps support their top-heavy beaks.
See also: Black hornbill, Blyth's Hornbill, Crowned hornbill, Great Indian Hornbill, Grey Hornbill, Malabar Grey hornbill, Northern Ground hornbill, Rhinoceros hornbill, Rufous hornbill, Silvery cheeked hornbill, Southern Ground Hornbill, Southern yellow-billed hornbill, Trumpeter Hornbill, Von der Deckens hornbill