HORNBLLL, the English name for a long while generally given to all the birds of the Family Bucerotidce of modern ornithologists, from the extraordinary horn-like excrescence (epithema) developed on the bill of most of the species, though to which of them it was first applied seems doubtful. Among classical authors Pliny had heard of such animals, and mentions them (Hist. Nat., lib. x. cap. lxx.) under the name of Tragopan; but he deemed their existence fabulous, comparing them with Pegasi and Gryphonesin the words of Holland, his translator (vol. i. p. 296)" I thinke the same of the Tragopanades, which many men affirme to bee greater than the iEgle; having crooked homes like a Ram on either side of the head, of the colour of yron, and the head onely red." Yet this is but an exag-gerated description of some of the species with which doubtless his informants had an imperfect acquaintance. Mediaeval writers found Pliny's bird to be no fable, for specimens of the beak of one species or another seem occasionally to have been brought to Europe, where they were preserved in the cabinets of the curious, and thus Aldrovandus was able to describe pretty fairly and to figure (Ornithologia, lib. xii. cap. xx. tab. x. fig. 7) one of them under the name of "Rhinoceros Avis," though the rest of the bird was wholly unknown to him. When the exploration of the East Indies had extended furthermore examples reached Europe, and the " Corvus Indicus comutus " of Bontius became fully recognized by Willughby and Ray, under the title of the " Horned Indian Raven or Topau called the Rhinocerot Bird." Since the time of those excellent or-nithologists our knowledge of the Hornbills has been steadily increasing, but it must be confessed that in regard to many points there is still great lack of precise information, and accordingly the completion of Mr Elliot's "Monograph of the Bucerotidae " (now in course of publication) is most earnestly to be desired, for therein it is to be hoped that all questions respecting their history and classification may be fully treated. At present great diversity of opinion prevails as to how many real genera the Family comprises, or how many species. The group, though no doubt ought to be enter-tained as to its limits, has not attracted sufficient notice from ornithologists, and therefore, apart from the merest superficial characters, the difference of the several sections which it includes has never been properly explained, nor have their distinctions been placed on a firm basis. Some authors appear to have despaired of dividing it satisfactorily, and have left all the described species in the Linnaean genus Buceros, as for example, Professor Schlegel (Cat. du Mus. des Pays Bos, Buceros); others have split that genus into more than a score a number which seems to be quite unnecessary. Sundevall (Tentamen, pp. 96, 97), with his usual caution, has restrained himself to the recognition of three genera, but it is unquestionable that more should reasonably be admitted, though the present writer is not prepared to state how many are required.
The first genus admitted by Sundevall is Bhinoplo.x, which seems properly to contain but one species, the Buceros vigil, B. scutatus, or B. galeatus of authors, commonly known as the Helmet-Hornbill, a native of Sumatra and Borneo. This is easily distinguished by having the front of its nearly vertical and slightly convex epithema composed of a solid mass of horn' instead of a thin coating of the light and cellular structure found in the others. So dense and hard is this portion of the "helmet" that Chinese and Malay artists carve figures on its surface, or cut it transversely into plates, which from their agreeable colouring, bright yellow with a scarlet rim, are worn as brooches or other ornaments. This bird, which is larger than a Raven, is also remarkable for its long graduated tail, having the two middle feathers nearly twice the length of the rest. Nothing is known of its habits. Its head was figured by Edwards more than a century ago, but little else had been seen of it until 1801, when Latham described the plumage from a specimen in the British Museum, and the first figure of the whole bird from an example in the Museum at Calcutta was published by Hardwicke in 1823 (Trans. Linn. Society, xiv. pi. 23). Yet more than twenty years elapsed before French naturalists became acquainted with it. Under Bhinoplax Sundevall places the Buceros comutus of Raffles; but this would seem to be a wrong position for that species, the type of Bonaparte's genus Bercnicornis, since it does not appear to possess a frontlet of solid horn.
Sundevall divides the genus Buceros into three sections, of which one, Buceros proper, contains the species having the epithema developed to its greatest extent, such as B. rhinoceros, B. hydro-corax, B. bieornis, and others, while the remaining sections have little or no epithema, and one of them has the throat feathered. This last includes the African forms which seem to belong to the genus Toccus of Lesson, while the other comprises the Oriental species exemplified by Mr Hodgson's genus Aceros; but the arrangement cannot be deemed wholly satisfactory, and must be regarded only as an approach to a better. The presence or absence of the epithema may indeed be considered in distinguishing genera; but among those that possess it, seeing that its development is to a great degree dependent upon age and perhaps sex (this last being uncertain), its size and shape hardly afford good generic characters, and, though the group assigned by Sundevall to Buceros proper doubtless requires further separation, some less superficial distinc-tions must be pointed out than those which have been taken as sufficient to establish many of the "genera" of this family sug-gested by several ornithologists. Again, in the grouping of those forms which possess little or no epithema sound characters are equally wanting for the divisions as yet set forth, and until further investigations have been made the limits of even the genera Aceros and Toccus cannot be laid down. Tickell in his manuscript Birds of India (in the library of the Zoological Society of London) divides the Hornbills of that country into two genera only, Buceros and Aceros, remarking that the birds of the former fly by alternately flapping their wings and sailing, while those of the latter fly by regular flapping only. Several differences of structure are pre-sented by the sternal apparatus of the various Bucerotidce, and it is quite possible that these differences may be correlated with Tickell's observations so as to furnish, when more is known about these birds, a better mode of classing them, and the same may be said of those of the African group containing the genus Toccus and its allies.
Lastly, we have the genus Bucorvus, or Bucorax as some call it, confined to Africa, and containing at least two and perhaps more species, distinguishable by their longer legs and shorter toes, the Ground-Hornbills of English writers, in contrast to all the preced-ing, which are chiefly arboreal in their habits, and when not flying move by short leaps or hops, while the members of this group walk and run with facility. From the days of Bruce at least there are few African travellers who have not met with and in their narra-tives more or less fully described one or other of these birds, whose large size and fearless habits render them conspicuous objects.
As a whole the Hornbills, of which more than 50 species have been described, form a very natural and in some respects an isolated group, placed by Professor Huxley among his Goccygomorphoe. It has been suggested that they have some affinity with the Hoopoes (Ujmpidce), but even if that view be good the affinity cannot be very near. Their supposed alliance to the Toucans (Rhamphastidoe) rests only on the apparent similarity presented by the enormous beak, and is contradicted by important structural characters. In many of their habits, so far as these are known, all Hornbills seem to be much alike, and though the modification in the form of the beak, aud the presence or absence of the extraordinary excrescence, whence their name is derived, causes great diversity of aspect among them, the possession of prominent eyelashes (not a common feature in Birds) produces a uniformity of expression which makes it impossible to mistake any member of the family. Horn-bills are social birds, keeping in companies, not to say flocks, and living chiefly on fruits and seeds ; but the bigger species also capture and devour a large number of snakes, while the smaller are great destroyers of insects. The older writers say that they eat carrion, but further evidence to that effect is required before the statement can be believed. Almost every morsel of food that is picked up is tossed into the air, and then caught in the bill before it is swal-lowed. They breed in holes of trees, laying large white eggs, and when the hen begins to sit the cock plasters up the entrance with mud or clay, leaving only a small window through which she receives the food he brings her during her incarceration.
This remarkable habit, almost simultaneously noticed by Dr Mason in Burma, Tickell in India, and Livingstone in Africa, and since confirmed by other observers, especially Mr Wallace in the Malay Archipelago, has been connected by Mr Bartlett (Proc. Zool. Society, 1869, p. 142) with a peculiarity as remarkable, which he was the first to notice. This is the fact that Hornbills at intervals of time, whether periodical or irregular is not yet known, cast the epithelial layer of their gizzard, that layer being formed by a secretion derived from the glands of the proventriculus or some other upper part of the alimentary canal. The epithelium is ejected in the form of a sack or bag, the mouth of which is closely folded, and is filled with the fruit that the bird has been eating. The announcement of a circumstance so extraordinary naturally caused some hesitation in its acceptance, but the essential truth of Mr Bartlett's observations has been abundantly confirmed by Professor Flower (torn, cit., p. 150), and especially by Dr Murie (op. cit., 1874, p. 420), and what seems now to be most wanted is to know whether these castings are really intended to form the hen bird's food during her confinement. (A. N.)
Such genera as Euryceros, Scythrops, and some others, together with the whole Family Momoiidce, which had been at various times and by various systematists placed among the Bucerotidce, have evi-dently no real affinity to them.
Apparently correlated with this structure is the curious thickening of the "proseneephalic median septum" of the cranium as also of that which divides the "proseneephalic" from the "mesencephalic chamber," noticed by Professor Owen (Cat. Osteal. Ser. Mus. Boy. Coll.
Surg. England, i. p. 287); while the solid horny mass is further strengthened by a backing of bony props, directed forwards and meet-ing its base at right angles. This last singular arrangement, which is not perceptible in the skull of any other species examined by the pre-sent writer, does not seem to have been described.
3 The noise made by the wings of some of the large species in their flight is compared by Mr Wallace, in an admirable article on the Family (Intellectttal Observer, 1863, pp. 310 et seqq.), to the puffing of a locomotive steam-engine when starting with a train, and can be heard a mile off.
j Button, as was his manner, enlarges on the cruel injustice done t > I these birds by Nature in encumbering them with this deformity, which
he declares must binder them from getting their food with ease. The only corroboration his perverted view receives is afforded by the observed fact that Hornbills, in captivity at any rate, never have any fat about them. The part played by the wonderful epitkema in the birds' economy is altogether unknown.
In his interesting work (i. p. 213), this gentleman describes a nestling Hornbill (B- bicornis) which be obtained as "a most curious object, as large as a pigeon, but without a particle of plumage on any part of it. It was exceedingly plump and soft, and with a semi-transparent skin, so that it looked more like a bag of jelly, with head and feet stuck on, than like a real bird."