National Geographic : 1999 Jul
NOT MANY PEOPLE would rec ognize the slit high in the trunk of the knobthorn tree as the entrance to a bird's nest. And nobody, unless he had a high-power telescope trained on the half-inch-wide opening, would see the gray-rimmed pupil peering through it. The youngster inside, an African red-billed hornbill, is hard at the keyhole of its new world, considering whether to fledge-which may not seem to be a particularly good idea in the penetrating drizzle of this dank morning in South Africa's Kruger National Park. Mother and father hornbill are nowhere to be seen, and that is by design-it is up to the youngster to peck its way to freedom. For this, nature has provided the bird with a powerful bill. The bill is an integral part of its skull, which is fastened to upper vertebrae that are fused and therefore stiff, creating, in effect, a feathered pickax. After observing its surroundings for many minutes, the bird begins to peck, and a hole is made. A head protrudes. The hornbill now has two eyes on the world, and it pauses for addi tional observation. More pecking, then head and right wing are free. Then-pop!--the magpie-size hornbill is out of the nest and fly ing to a branch, where it sits, once again taking the measure of its surroundings. But how did the bird get in the nest in the first place? The answer is one of the great tales of animal behavior, for most hornbill females make unique nests in tree cavities, using their bills to wall themselves in with a plaster made of mud, droppings, chewed wood and bark, and other detritus. They leave only a slit, nar row enough to deter predators but sufficiently wide for the male to present food from the out side. After a few months, having laid and incu bated their eggs, the females peck a hole in the wall and leave. The chicks wall themselves back in, to fledge at their leisure. The hornbill universe, with initial entries appearing in the fossil record some 15 million years ago, comprises 54 species of birds. Their range includes most of sub-Saharan Africa and extends east to the forests of Southeast Asia and the Solomon Islands. Africa is home to the largest and the loudest -the nine-pound southern ground hornbill's deep bass call booms as far as two and a half miles, about the same distance a lion's roar car ries. The African dwarf red-billed, smallest of hornbills, is the size of a dove. Hornbills possess magnificent beaks-more than 13 inches long on one great pied hornbill -which they wield like forceps to grasp and toss insect prey in the air, then with impressive coordination catch it in their gullets. Bills are also used to poke among branches for fruit or even to keep a poisonous snake at bill's length to protect vulnerable body parts. Many hornbills wear on their beaks a horny, some times spectacular crownlike protrusion called a casque, hollow except for the nearly solid, ivorylike casque of the helmeted hornbill. Whence, presumably, the name. Examining a tropical bird whose casque had two peaks, the taxonomist Linnaeus in 1758 bestowed the scientific name Buceros, Latin for "having ox's horns." This probably accounts for the common name; at least it will do until a better explanation comes along, says my companion Alan Kemp, an ornithologist and curator of birds at the Transvaal Museum in Pretoria. Kemp suggests we prowl for more hornbills. By park regulations we are obliged to remain in our truck, lest one of Kruger's 2,000 lions decide to take advantage. We drive past ele phants, giraffes, warthogs, white rhinos slightly smaller than tanks and are delayed for a time by a roadblock of lounging lions. Farther along Kemp picks up a squirrel killed on the road and puts it on the backseat. Later in the afternoon a group of southern ground hornbills crosses the road and heads into the bush. The dark-bodied birds walk deliberately through the long grass with their heads canted downward, in the manner of cowled monks proceeding to choir. There are seven, about the size of turkeys, wearing red skin folds around their heads and throats and Room service: A red-knobbed hornbill arrives with breakfast, which he will regurgitate for his roughly three-month-old chick safely inside a nest hole in an Alstonia tree. Though its mother has left the confines of the nest, the chick remains within for another few weeks, dependent on its parents until it fledges.