Hornbills are easily identified from their distinctive large, curved and long – yet light – beak. There is a structure on top of their beaks that is unique to hornbills: the casque. Different hornbill species have different plumage color and casque shape, size and color.
Most casques are hollow and function as resonator for calls. The helmeted hornbill however, have a more solid casque.
Hornbills are large birds with body length of 65-170 cm and weighing 290-4,200 g. Males have brighter plumage and larger bodies than females. Their bodies are almost entirely covered by feathers of various colors: black, gray, white or other colors (yellow and red) on their necks, heads, and around the eyes.
Adult hornbills are sexually dimorphic and can be distinguished by the color of their casques, wings, beaks, eyes, and body size. In addition to their morphology, hornbills can be identified from their calls and wing flaps.