Colours of Wildlife: Rhinoceros Hornbill
Created | Updated Oct 16, 2016
Rhinoceros Hornbill
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
On we go with my odyssey to portray all of the world’s hornbill species! This one is a small watercolour painting of a Rhinoceros Hornbill, Buceros rhinoceros. The scientific name means 'ox-horn nose-horn'. It is one of four (or perhaps five) very large Asian hornbill species constituting the genus Buceros, and definitely one of the most spectacular hornbills – heck, one of the most spectacular birds in the world. This species reaches an overall length of 90 cm/3' and a weight of about three kg/6.5 lbs. There are three subspecies, with varying curvatures to the 'horn' (actually called a 'casque') on top of the bill. But all of them are awesome! Males and females are unusually similar in comparison with other species where the females have much smaller casques. Rhinoceros hornbill females are only slightly smaller than the males and have white eyes, where the male's eyes are deep red. Rhinoceros hornbills live in the wild in rainforests on the tip of the Malaysian Peninsula, and on the great islands of Sumatra, Java, Borneo and a few small ones in the same region.
I've already said much about hornbills in my other hornbill articles, which you can reach by clicking on the link to the Colours of Wildlife Archive. This species, like other hornbills, nests in cavities in trees (but very occasionally in cliffs). The female will often dig at the hole with her powerful bill to enlarge the cavity or shape it to make it more comfortable for herself. Because of the size of these hornbills, they are dependent on very big trees in which big enough cavities can form. Courtship includes the male chasing the female around, bringing her food in a ritualized manner, and the couple 'fencing' with their bills. They mate very frequently, chattering nasally as they do so. When she's ready to lay her eggs, the female 'imprisons' herself – she seals up the entrance hole of the cavity from the inside, using her own dung which dries out hard. She only leaves a slit for the tip of her bill to poke through. Now, from the outside, the male brings her food. She lays one or two eggs and hatches out the chick/s, at which point the male has to provide food for them. All through this, the female keeps her nest scrupulously clean. She will press her butt up to the entrance hole and squirt her droppings out forcibly; when the chick/s are there, she will pick their droppings up with her bill and throw them out. She will also throw out any scraps of uneaten food, or large seeds which she or the chicks regurgitate. The chicks might sometimes eat some of their own droppings. This might be, as with rabbits, to 'double-digest' food to improve their chance of absorbing its nutrition.
Hornbill eggs hatch after about 37-46 days; the chicks spend another 78-80 days in the nest, but the female leaves when they still have four to seven weeks to go. She breaks out and immediately re-seals the entrance hole. Now she and the male feed the chick/s together, making the job a bit easier. They feed them mainly on figs and other jungle fruits, but also some insects such as grubs and crickets. The feeding adult gathers lots of food in its gullet which swells up visibly, and then regurgitates it for the chick/s. If the nestling dies, the female can be ready soon to lay a replacement clutch. Even after they fledge, the parents keep feeding the chicks, for six months or even more. This slow-growing species probably breeds only one every two years or so. But a bird grown to adulthood may live to the age of ninety years!
Adult hornbills occur as couples, sometimes attended by some of their adult offspring. They are territorial and have large ranges. Sometimes they form flocks of up to 25 birds, mainly composed of sub-adults or adults not yet breeding. They fly over the forest canopy with noisy wingbeats. They sometimes perch exposed in a high tree to sunbathe. They also like bathing using water drops clinging to leaves after rains. They eat mainly fruit: about half being figs, rich in sugars, and the other half being oily fruit or hard seeds. At fruit trees, their size and strength help them to chase away all other competing species. They also eat invertebrates and small reptiles, mammals and birds – also bird eggs. Most of the time they feed in the canopy, but sometimes they descend to the ground to hunt small critters or to pick up fallen fruits.
In this species, the casque on the bill is very big and conspicuous and likely is a feature that both the male and female find attractive. The casque is hollow and lighter than it looks, with a network of thin, bony struts inside to reinforce it. As in other hornbills, it might also help to amplify the hornbill's calls. This is quite a vocal species. The male and female, as in some other bird species, sing a duet together. The male sings a short, deep 'hok' note, which the female follows with a higher 'hak' note, and so they go on … 'hok-hak-hok-hak-hok-hak…' Each bird jerks its head upward and raises the bill on every note. This call helps the couple to bond. They will even duet while the female is imprisoned in the nest. They give a nasal 'ger-ronk' call in flight, and again the female and the male will usually alternate their calls. This call carries over several km/miles and probably plays a territorial role. The female also calls with a high, thin 'eeee…' when the male brings her food in the nest. The chicks peep when they're being fed. If the female is disturbed in the nest, she will squeal harshly, and the male will give a nasal alarm call at the nest if there's something dangerous in the environment. The male also sometimes grunts when he leaves the nest to go seek more food. In the ritual of food-giving, the female gives a strange coughing sound as she accepts it from the male.
Other displays of this species includes a vigorous bouncing up-and-down on a perch, as a threat towards other hornbills or predators. This bouncing motion is imitated in the dances of the Dyak people of Borneo, for whom the bird is of much ceremonial significance.
The rhinoceros hornbill is the emblem of the Malaysian state of Sarawak (on the island of Borneo). The Iban people carve effigies in the shape of hornbills, and th Dyaks (mentioned above) collect them for their feathers, which they make into headdresses and capes, and heads and casques which they preserve. They also sometimes keep them as pets.
This species, like many others from rainforests, is threatened, mostly by habitat destruction. This is happening more and more in Southeast Asia as human populations continue to grow, and as many people chop down forests to turn into oil-palm plantations. We humans really need to figure out how to co-exist with this and other species … if we lose them, it would be grievous for us as well as for them. And for the rainforests themselves, since as distributors of the seeds of fruiting trees, they play a vital role in sustaining the overall tree diversity.
