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The horn of the hornbill: what’s it for?

Hornbills are a fascinating group of birds. While these long-beaked animals might superficially resemble toucans, the hornbill family (Bucerotidae) is not closely related to the toucan family at all!

The hornbill family contains a diverse number of species, three of which are housed here at Zoo Atlanta. While many Asian species subsist on a diet of fruits and insects, the African species (the ground hornbills) spend most of their time walking on the ground and are strictly carnivores. Regardless of what they eat, all hornbills have poorly developed tongues, so rely on a feeding mechanism called “ballistic transport,” in which food is tossed from the tip of the beak into the back of the throat.

The “horns,” or casques, of hornbills are actually extensions of the upper beak and are just as diverse as hornbill species themselves. The casques of ground hornbills are small and poorly developed compared to other hornbills. In rhinoceros hornbills, the casque is immense and extends nearly as far forward as the upper beak but is almost entirely hollow on the inside! Helmeted hornbills have casques that are almost completely solid and resemble ivory in texture.

So, what is the purpose of those impressive casques? The answer is that nobody knows for certain! In some species like the helmeted hornbill, the casque is thought to be used in combat, as these birds often engage in a behavior called aerial jousting. In other species, the purpose is less clear. Hypotheses range from use as an ornamental structure (for example, attracting a mate), reinforcement of the beak for high impact pecking behaviors, or use as a resonance chamber to help vocalizations carry farther.

Despite the beauty and impressiveness of the casque, problems can arise from this structure. Traumatic injuries, infections, and even cancers have all been described in the casques of both wild hornbill species and hornbill species in human care. As their care team, our job is to monitor these animals closely for any signs of things out of the ordinary.

So, what do you think the hornbill’s horn is for? Next time you’re at the Zoo, take a close look at all the different magnificent hornbill species that we care for here and decide for yourself!

Sam G.
Keeper I, Birds

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