This section is from "The American Cyclopaedia", by George Ripley And Charles A. Dana. Also available from Amazon: The New American Cyclopędia. 16 volumes complete..
Hornbill , (buceros, Linn.), a genus of coni-rostral birds of Africa and the East Indies, of the family bucerotidoe. The principal genus buceros is characterized by an enormous bill, long, broad, curved, surmounted by helmetlike prominences of various sizes and shapes, with compressed sides and acute tip; the lateral margins are more or less jagged and serrated in the adult; the nostrils are basal, lateral, and small; the wings are rather short, with the third quills nearly as long as the fourth and fifth, which are equal and longest; tail long and broad, more or less graduated; tarsi short, robust, covered in front by large transverse scales; toes broad and long, and united at the base so as to form a kind of sole; the hind toe large and flat, giving a firm support in their leaping mode of progression; claws long, curved, and sharp. The face and throat are more or less naked, sometimes with a gular pouch; above the eyes are a few bristly hairs, like lashes; the tongue is small and cartilaginous. Nearly 40 species are described, in which the bill, always large, has a great diversity of form, varying in its protuberances according to age; bulky though it be, it is of a light and cellular structure, and by no means the formidable weapon its size would indicate; its awkward shape and slight mechanical support render it difficult for the bird to manage except for seizing objects requiring slight force; its thin edges, broken by use, undergo a constant process of repair.
Most of the species are of large size; they are observed singly or in parties, in the dense jungles and woods, perched on the highest branches, especially on decayed limbs near rivers; they feed upon pulpy fruits, small quadrupeds, birds, reptiles, and insects, which they crush with the bill, and, after tossing them into the air, swallow whole; when hard pressed they will not refuse carrion. The flight is heavy and straight, generally at a considerable height, and accompanied by a remarkable noise; the cries are hoarse croaks or harsh screams; the nest is hollowed in a decayed tree, and the eggs are about four. The largest species is the rhinoceros hornbill (B. rhinoceros, Linn.), nearly 4 ft. long, with an expanse of wings of about 3 ft.; the bill is nearly a foot long, the upper mandible having a recurved prominence like a rhinoceros horn, giving the head the appearance of being top-heavy; the general color is black, the tail being tipped with dirty white; the bill is black at the base, reddish in the middle, and light yellow at the point. It is a stupid and cowardly bird, seldom showing any vivacity except when in search of food; it is found in India and its archipelago, and is common in collections of natural history; it is voracious, and in' captivity is decidedly omnivorous.
The red-billed hornbill (B. erythrorhynchus, Temm.), a native of Africa, like the rest of the genus, breeds in hollow trees; it occupies holes, according to Livingstone, in the mopane tree (Bauhinia), a very hard wood; the female makes her nest in February, lining it with her own leathers, and lays four or live eggs, of the size of a pigeon's, and of a white color; she remains a close prisoner in the hole until the young are fully fledged, a period of eight or ten weeks; during this time the opening is plastered up with clay by the male, with the exception of a slit three or four inches long and about half an inch wide, exactly fitting the shape of his beak, and through this he feeds the female and the young. While thus imprisoned she gets very fat, and is esteemed by the natives a dainty morsel; they often dig her out, letting alone the lean and overworked male. The female sometimes hatches out two young, and by the time these are fully fledged two others are just out of the egg; she then leaves the nest with the two oldest, and the hole is again plastered up, both parents attending to the wants of the remaining young until they too are able to come forth.
Rhinoceros Hornbill (Buceros rhinoceros).
Red-billed Hornbill (Buceros crythrorhynchus).
 
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