Wrinkled Hornbill

The wrinkled hornbill, also called the Sunda wrinkled hornbill, is a medium-large hornbill found in forest in the Thai-Malay Peninsula, Sumatra and Borneo. It is around 70 cm long, with mainly black plumage, a blue eye-ring and a very large bill fused to the skull. Males have bright yellow feathers on the cheeks, throat and chest, which are black in females, and the male's bill is yellow with a red base and casque. It eats mainly fruit such as figs, along with small animals such as frogs and insects, and gets the water it needs from its food. Pairs remain together for life.

About the wrinkled hornbill

The wrinkled hornbill (Rhabdotorrhinus corrugatus), also called the Sunda wrinkled hornbill, is a medium-large forest hornbill of Southeast Asia, found on the Thai-Malay Peninsula, Sumatra and Borneo. It belongs to the hornbill family, Bucerotidae, and its closest relatives are three other Asian hornbills in the genus Rhabdotorrhinus.

Those relatives are the rufous-headed hornbill, the writhed hornbill and the Sulawesi hornbill. A molecular study found that these four species form their own group, more closely related to the genus Penelopides than to the hornbills they were once lumped with in the genus Aceros. That is why the four are now classified together in the separate genus Rhabdotorrhinus.

The wrinkled hornbill is about 70 cm (28 in) long. Its plumage is mostly black, with a blue ring of bare skin around the eye and a broadly white or rufous-tipped tail. It has a very large bill that is fused to the skull and topped by a casque, a horny structure on the upper bill.

Males and females are easy to tell apart. Males have bright yellow feathers on the ear coverts, cheeks, throat, sides of the neck and chest. Their bill is yellow with a red base and a red casque, and the base of the lower bill is brownish. In females those same areas are black, except for a blue throat, and the bill and casque are almost entirely yellow.

As in other hornbills, the heavy bill is supported by strong neck muscles and by the first two neck vertebrae, which are fused together. Hornbills are the only birds with this feature. Hornbills also have binocular vision in which the bill tip is visible to the bird, helping it handle food precisely, and long eyelashes that shade the eyes. The casque is a hollow structure along the upper bill; in some hornbills it is barely noticeable, while in others it is large, reinforced with bone and works as a resonator for calls.

Behavior and diet

The wrinkled hornbill is a forest bird that eats mainly fruit, especially figs. It also takes small animals, including frogs and insects. Remarkably, it does not drink. It gets all the water it needs from its food.

Hornbills as a family are diurnal. They cannot swallow food held at the bill tip because their tongues are too short to move it, so they toss each item back into the throat with a flick of the head. Forest-dwelling hornbills in general are considered important seed dispersers.

The wrinkled hornbill has two main calls: a harsh "kak-kak" and a deep "row-wow" that can carry for miles.

Pairs are monogamous and stay together for life. They nest in holes in trees. Once the female is inside, she plasters the entrance with mud and droppings until only a small slit remains, too narrow for her or the chicks to get out. The male then feeds the whole family by himself, regurgitating food through the gap. In hornbills generally, the female goes through a full molt while sealed in the nest. In hornbills, sealing the entrance takes anywhere from a few hours to a few days, and the first egg is laid about five days later. After several months, when the chicks are ready, the female breaks out of the nest.

The species was first bred in captivity in 1988.

Range and habitat

The wrinkled hornbill lives in the forests of the Thai-Malay Peninsula, the island of Sumatra and the island of Borneo. It is a forest species that nests in holes in trees.

Its range lies in a region rich in hornbill species. Indonesia as a whole has 13 hornbill species, nine of them on Sumatra, and the Indonesian part of Borneo, Kalimantan, has the same species as Sumatra except the great hornbill. Another Bornean hornbill is the rhinoceros hornbill, the state animal of Sarawak, which the Iban people of Borneo regard as the king of worldly birds.

Wrinkled hornbill vs writhed hornbill

The writhed hornbill, also called the Mindanao wrinkled hornbill, is a close relative in the same genus. The names are easy to confuse, but the birds live on different islands.

Both belong to the hornbill family, which has about 62 living species ranging from the black dwarf hornbill, at 32 cm (13 in), to the southern ground hornbill.

Conservation status

The wrinkled hornbill is listed as Endangered on the IUCN Red List. It was moved up from Near Threatened to Endangered in 2018 because of heavy deforestation in its forest habitat.

Its situation reflects a wider pattern. No African hornbills are seriously threatened, but many Asian species are at risk from hunting and habitat loss because they need primary forest. Forest hornbills in general nest in natural tree cavities, and fruit-eating species travel long distances between patchy fruit sources, so clearing forest removes both nest sites and food.

The wrinkled hornbill's own genus shows how serious the pressure can be. Its relative the rufous-headed hornbill, restricted to the Philippines, is one of only three hornbill species rated Critically Endangered, and the writhed hornbill is Near Threatened with a declining population.