Hornbills

With their long curved bills and jaunty disposition, hornbills are among the most conspicuous of African birds, and also among the most interesting. Although not brightly coloured - most have black, white or grey plumage - many species have colourful bills or bare facial skin, and all are striking birds. The males of many species possess a raised section on the upper mandible, known as a casque, and this probably plays some role in display or mate selection.

Hornbills are confined to the tropics of the Old World, with 25 species in Africa and 20 in south-east Asia. No hornbills occur on the islands of Australia or Madagascar. The toucans of central and south America share several physical traits with hornbills, but are not closely related. In Africa, hornbills have adapted to survive in habitats ranging from the wettest rainforests to the fringes of the arid Namib Desert, but they are best represented in forests and savannah, where an abundance of nesting cavities and food is to be found. For birdwatchers, they are among the most sought after birds and many are quite confiding and easily photographed; they are therefore an attraction in many eco-tourism ventures.

Frugivores

Frugivores are animals that feed primarily of fruit, as insectivores feed primarily on insects. The Trumpeter, Black-and-white-casqued, and Silvery-cheeked Hornbills are fruit specialists that favour figs above harder fruits, and it is always entertaining to watch these large, rather comical-looking birds plucking at tiny figs with their over-sized bill. Closer study reveals that the beak actually allows these birds to reach the tips of branches that could not support their weight, and also that they are used as forceps to test the ripeness of individual fruits before they are plucked, tossed into the air, and swallowed. These large hornbills will feed on small animals when the opportunity presents itself, but gain most of their nutrition from figs and other fruit.

Insectivores and Carnivores

Although they may take fruit from time-to-time, the Yellow-billed, Von der Decken's, African Grey, White-crested and Crowned are examples of hornbills that feed primarily on insects and small vertebrates such as lizards and nestling birds. The Yellow-billed Hornbill is often seen around the dung middens of rhino and fresh elephant droppings where it feasts on dung beetles, while the Crowned Hornbill is adept at dealing with dangerous wasps and noxious caterpillars.

The extraordinary White-crested (or Long-tailed) Hornbill lives in equatorial rainforest, with family groups typically following troops of foraging monkeys to snap up the insects that are disturbed by the boisterous primates. The huge Southern Ground Hornbill can be regarded as a true carnivore for it feeds voraciously on all manner of creatures from venomous snakes to small mammals, and even scavenges from the carcasses of wildebeest and other large animals. This distinctive black and white hornbill is particularly fond of stalking through recently-burnt bushveld where it feeds on the grilled corpses of tortoises, chameleons and other creatures that were unable to escape the flames.

Paired for Life, but Entombed for Birth

Like vultures and albatrosses, hornbills appear to pair for life, and an understanding of their extraordinary breeding behaviour - in which each sex has a distinct and demanding role - provides the reason for this.

All hornbills are hole-nesters, and it is fairly well-known that the female typically seals herself into the nesting cavity once her clutch of eggs has been laid. She cements herself in with mud and excreta, leaving just a tiny slit through which food can be passed. Once safely ensconced, she undergoes a complete moult of her flight feathers - a "make-over", if you will - and becomes reliant upon her mate who is tasked with the job of keeping his partner fed during the several weeks of incubation. Such responsibility could hardly be expected of a less committed partner! For the male, his own genetic investment is vested with his mate and it is therefore important that he sees her through this tricky but secure phase of the breeding cycle.

Once the nestlings assume their own feathers, the female breaks out of the chamber and joins her mate in provisioning the youngsters with food. They, in the meantime, re-seal the nest hole and develop rapidly before chipping their way to freedom - a process that may take several days.

Spiritual Connections

Because of their striking appearance, haunting calls and secretive nesting habits, hornbills feature prominently in the cultures, folklore and ceremonies of many human societies. The Southern Ground Hornbill, for example, is regarded as a wise spirit and although it is featured in Zimbabwean cultural songs and dances, it is considered unwise to talk about the bird for fear of retribution. In the Transkei area of South Africa, this hornbill is held sacred and must never be harmed; should one be killed, the culprit is obliged to sacrifice a calf or young ox in atonement. Perhaps because of its deep booming call - not unlike the throaty moan of a lion, or distant thunder - the Ground Hornbill is also regarded as a forebearer of rain. In Cameroon, the skull and bill of the Northern Ground Hornbill is worn as a head-dress by tribesmen when hunting.

Conservation

Although hornbills may be rather common in some environments, their status is easily affected by the disappearance of suitable trees in which to breed. In parts of Africa where fuel is in short supply, dead trees are seldom left standing outside of protected areas and hornbills soon disappear from the scene. Logging in equatorial rainforest similarly affects the larger species which often rely on cavities in the tallest available trees. As with so many other species in Africa, their long-term survival will depend largely upon the attitude of the local people who need to have their own reasons - whether economic or spiritual - to ensure that hornbills continue to share their world.

Further Reading
Kemp, A. 1995. The Hornbills.
    Oxford University Press, Oxford.

Posted: Birds by CC Africa, Date: 21 November 2006