Birds
Great Hornbill
Buceros bicornis · also called great hornbill, great indian hornbill, concave-casqued hornbill
The great hornbill is one of the largest and most imposing birds of the Asian rainforest: a metre of black-and-white plumage under a massive yellow bill, topped by a hollow casque. Its wingbeats puff and roar loudly enough to hear from hundreds of metres away, and when it nests, the female shuts herself inside a tree hole for months and lets the male feed her through a slit.
Overview
Great hornbills live in the forests of the Indian subcontinent and mainland Southeast Asia, from the Western Ghats to Sumatra. They are 95–120 cm long with a wingspan near 1.5 m, black and white with a huge yellow bill and casque. They eat mostly fruit, especially wild figs, plus large insects and small animals, and are among the most important seed dispersers of big rainforest trees.
The casque and the wingbeats
The bright U-shaped casque is mostly hollow over a light bony lattice; its role is debated — amplifying calls, signalling age and fitness, and cushioning head-to-head clashes between males have all been proposed. The rushing sound of the wingbeats, made by air passing gaps at the base of the flight feathers, announces the bird before it is seen.
The sealed nest
The female enters a tree cavity and, helped by the male, walls up the entrance with mud and droppings until only a narrow slit remains. She stays inside for three to four months, moulting all her flight feathers, entirely dependent on the male passing food through the gap, until the chicks are large.
Status
The great hornbill is Vulnerable and declining, hit by loss of mature forest with big fruiting and nest trees, and by hunting for meat, casques, and feathers. It is the state bird of Kerala and culturally important across its range.
Great Hornbill: common questions
What is the great hornbill's casque for?
The casque is the large hollow structure sitting on top of the bill, and despite its size it is very light, built from a thin bony framework filled mostly with air. Several functions have been suggested and it may serve more than one. It could act as a resonating chamber that amplifies and lowers the bird's loud calls, helping them travel through dense forest. It is larger and more richly coloured in older birds and in males, so it probably signals age, condition, and sex to rivals and mates. And males sometimes clash in flight, striking casque against casque, so it may also work as a buffer or a weapon in those contests.
Why does the female hornbill seal herself inside the nest?
It is a defence for the eggs and chicks. Great hornbills nest in tree holes, which are attractive to snakes, monitor lizards, civets, and other hornbills looking to take over the site. By walling up the entrance from the inside until only a slot remains, the female makes the nest almost impossible for a predator to enter, and she also creates a controlled environment for incubation. The cost is that she and later the chicks are entirely dependent on the male to deliver enough food through the slit for months, so the system only works where fruit is abundant and the male is a reliable provider. If the male dies, the family inside usually dies too.
How important is the great hornbill to the forest?
Very. It is one of the largest fruit-eating birds in Asian rainforests, it travels long distances every day between fruiting trees, and it swallows fruit whole and later drops or regurgitates the seeds intact, often far from the parent tree. This makes it a key disperser for many large-seeded forest trees, some of which have few other animals capable of moving their seeds. Where great hornbills are hunted out or lose their habitat, the regeneration of those tree species can decline, so conservationists sometimes describe the bird as a forest gardener or a keystone species.
Is the great hornbill endangered?
It is listed as Vulnerable, a step below endangered, and its numbers are falling. The main problems are the loss and fragmentation of the mature lowland and foothill forest it needs, because it requires very large old trees both for fruit and for nest cavities, and hunting. The birds are killed for meat, for the casque and bill, which are carved or worn, and for tail feathers used in traditional dress. Conservation efforts include protecting large forest reserves, safeguarding known nest trees, artificial nest boxes, and working with communities that have a cultural connection to the bird to shift from hunting to protection.