| Great Hornbill | |
|---|---|
| Perched on a Mesua tree at Valparai, South India | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Coraciiformes |
| Family: | Bucerotidae |
| Subfamily: | Bucerotinae |
| Genus: | Buceros |
| Species: | B. bicornis |
| Binomial name | |
| Buceros bicornis Linnaeus, 1758 |
|
| Synonyms | |
|
Buceros homrai[2] |
|
The Great Hornbill (Buceros bicornis) also known as Great Indian Hornbill or Great Pied Hornbill, is one of the larger members of the hornbill family. Great Hornbills are found in the forests of Nepal, India, the Malay Peninsula and Sumatra, Indonesia. Their impressive size and colour have made them important in many tribal cultures and rituals. The Great Hornbill is long-lived, living for nearly 50 years in captivity. They are predominantly frugivorous although they are opportunists and will prey on small mammals, reptiles and birds.
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The Great Hornbill is a large bird, 95–120 cm (38–47 in) long, with a 152 cm (60 in) wingspan and a weight of 2.15–4 kg (4.7-8.8 lbs). It is the heaviest, but not the longest, Asian hornbill. The most prominent feature of the hornbill is the bright yellow and black casque on top of its massive bill. The casque appears U-shaped when viewed from the front and the top is concave with two ridges along the sides that form points in the front, a reference to which is made in the Latin species epithet bicornis. The casque is hollow and serves no known purpose although they are believed to be the result of sexual selection. Male hornbills have been known to indulge in aerial casque butting, with birds striking each other in flight.[3] Females are smaller than males and have bluish-white instead of red eyes although the orbital skin is pinkish. Like other hornbills, they have prominent "eyelashes". The back of the casque is reddish in females while the underside of the front and back of the casque is black in males. The male spreads the preen gland secretion which is yellow onto the primaries and bill to give them the bright yellow colour.[4] The commissure of the beak is black and has a serrated and worn edge with age. The wing beats are heavy and the sound produced by birds in flight can be heard from a distance. The sound produced has been likened to the puffing of a steam locomotive starting up. The flight involves stiff flaps followed by glides with the fingers splayed and upcurled. They are sometimes known to fly at great height over forests.[5][6]
The species was formerly broken into subspecies cavatus from the Western Ghats, nominate form from the sub-Himalayan forests is sometimes named as subspecies homrai. The subspecies from Sumatra has sometimes been considered as cristatus.[7] The variation across populations is mainly in size, with Himalayan birds being larger than the those from further south and the species is now usually considered monotypic.[8][9]
Like other members of the hornbill family, they have highly pneumatized bones, with hollow air cavities extending to the tips of their wing bones. This anatomical feature was noted by Richard Owen who dissected a specimen at the Zoological Society of London that died in 1833.[10]
The distribution of the species is fragmented over its range in South and Southeast Asia. In South Asia they are found in a few forest areas in the Western Ghats and in the forests along the Himalayas. Their distribution extends into Thailand, Burma, Malaya and Sumatra.[11] Their habitat is dense old growth (unlogged) forests in hilly regions.[12][13] They appear to be dependent on large stretches of forest unlike many of the smaller hornbills.[14]
In Thailand the home ranges of males was found to be about 3.7 km² during the breeding season and about 14.7 km² during the non-breeding season.[15]
Great Hornbills are usually seen in small parties with larger groups sometimes aggregating at fruit trees. A congregation of 150 to 200 birds has been recorded in southeastern Bhutan.[5] In the wild, the Great Hornbill's diet consists mainly of fruit. Figs are particularly important as a food sources.[16] Vitex altissima has been noted as another important species. They also forage on lipid-rich fruits of the Lauraceae and Myristicaceae families such as Persea, Alseodaphne and Myristica.[17] They obtain the water that they need entirely from their diet of fruits. They are important dispersers of many forest tree species.[18] They will also eat small mammals, birds,[19] small reptiles and insects.[20] It has been observed that lion-tailed macaques forage alongside these hornbills.[21]
They forage along branches, moving along by hopping, looking for insects, nestling birds, small lizards, tearing up bark and examining them. Prey are caught, tossed in the air and swallowed. A rare squirrel, the Travancore flying squirrel Petinomys fuscocapillus has been noted in the diet of the species while Collared Scops Owl Otus bakkamoena, Jungle Owlet Glaucidium radiatum and Grey-fronted Green Pigeon Treron pompadora have been noted as prey birds in the Western Ghats.[22]
During the breeding season they become very vocal. They make loud duets. These calls begin with a loud "kok" about once a second given by the male and joined in by a female. The pair then calls in unison turning into a rapid mixture of roars and barks.[22] They prefer mature forests for nesting. Large, tall and old trees, particularly emergents that rise above the canopy appeared to be preferred for nesting.[23][24]
The Great Hornbills form monogamous pair bonds and live in small groups of 2-40 individuals. Group courtship displays involving up to 20 birds have been observed.[25]
Female hornbills build nests in hollows of large tree trunks and the opening is sealed with a plaster made up mainly of feces.[7][26][27] She remains imprisoned in her nest until the chicks are semi-developed relying on the male to bring her food. During this period the female undergoes a complete moult. The young squabs are devoid of feathers and appear very plump. She is fed by her mate through a slit in the seal. The clutch consists of one or two eggs she incubates for 38–40 days. The female voids faeces through the nest slit and young follow the same nest sanitation behaviour after they are two weeks old.[22] Once the female emerges out of the nest, it is sealed again by the chicks.[8]
The young birds have no trace of a casque. After the second year, the front extremity separates from the culmen and in the third year becomes a transverse crescent with the two edges growing outwards and upwards while the anterior gets broader to equal the hind end in width. The full development takes five years.[28]
Roost sites are used regularly and birds will arrive punctually at sunset from long distances, following the same routes each day. Several tall trees in the vicinity may be used, the birds choosing the highest branches with little foliage. They jockey for positions until late at dusk. When sleeping they draw their neck back and the bill is held upwards at an angle.[5]
Very few hornbills are held in captivity and few of them breed well. The females at the nests are extremely easy to capture and wild caught birds are female biased. Breeding them in captivity has been notoriously difficult with fewer than a dozen successful attempts. Their extreme selectivity for mates and the long and strong pair bonds make them difficult to maintain for breeding.[29][30][31][32]
In captivity hornbills eat fruits and meat and a healthy diet is made up in most part, by fruit and some source of protein. A few have been tamed in captivity but hornbill behavior in captivity is described as high-strung. Captive specimens may bask in the sun with outstretched wings.[33]
Due to habitat loss and hunting in some areas, the Great Hornbill is evaluated as Near Threatened on the IUCN Red List of Threatened Species.[1] It is listed on Appendix I of CITES. Declines in population have been noted in many areas such as Cambodia.[34] Molecular approaches to the study of their population diversity have been attempted.[35]
Tribals threaten the Great Indian Hornbills with their desire for its various parts. The beaks and head are used in charms and the flesh is believed to be medicinal. The squabs are considered a delicacy.[5] Tribesmen in parts of northeastern India and Borneo use their feathers for head-dresses, and their skulls are often worn as decorations.[36][37] Their flesh is considered unfit for eating by the Nagas with the belief that they produce sores on their feet as in the bird. When dancing with the feathers of the hornbill, they avoid eating vegetables as it is also believed to produce the same sores on the feet.[38] Conservation programmes have attempted to provide tribes with feathers from captive hornbills and ceramic casques to substitute natural ones.
The hornbills is called "homrai" in Nepal (giving the name of that subspecies) and "banrao" both meaning "King of the forest".[39]
The Great Hornbill is the State bird of Chin state in Myanmar, and Kerala and Arunachal in India.
A Great Hornbill by the name of William (pictured) was the model for the logo of the Bombay Natural History Society (BNHS). BNHS headquarters billing is called Hornbill House. Sir Norman Kinnear described William as follows in the obituary of W S Millard: “Every visitor to the Society's room in Apollo Street will remember the great Indian Hornbill, better known as the "office canary" which lived in a cage behind Millard's chair in Phipson & Co.'s office for 26 years and died in 1920. It is said its death was caused by swallowing a piece of wire, but in the past "William" had swallowed a lighted cigar without ill effects and I for my part think that the loss of his old friend was the principal cause." [41][42]