What is a Hornbill’s Casque For?
It’s hard to imagine what the bulky casque on the upper bill of a hornbill is there for. In most cases it’s not as heavy as it looks: it’s composed of keratin, the same material that human fingernails are made of, and it’s hollow, with only slender supports inside. The Helmeted Hornbill’s casque is an exception: the front of the casque in this species is a heavy chunk of keratin called hornbill ivory. Scientists think that hornbill casques have various functions, and these differ between species: • In some species the casque simply makes the top part of the beak stronger. • Casques are ornamental in some species, presumably communicating information about the bird’s age and sex to potential mates. • When the interior of the casque is open to the interior of the beak, as it is in the males of some African species, it may affect the sound of the bird’s call, making the call loud and nasal. • Large casques might be used to knock fruit down from trees, or for digging. • In species such as
