Buceros bicornis
great hornbill

Buceros bicornis is found in mainland Southeast Asia, the Malay Peninsula and Indonesia. They are breeding residents in Bhutan, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand and Vietnam. In India, they and several other hornbill species live in the Western Ghats mountain range and forests in both the northeastern and southern regions. ("Endangered Animals of Thailand", 1990; "Popular Handbook of Indian Birds", 2007; Datta, 1998; Mobley, 2008; Raman and Mudappa, 2003)

Great hornbills are arboreal and live mainly in wet, tall, evergreen forests. Old-growth trees that extend beyond the height of the canopy are preferred for nesting. The height of the tree and the presence of a natural cavity large enough to hold a female and her eggs are more important than the type of tree. The same nesting site is used year after year if possible. They are known to inhabit elevations of 600 to 2000 m. ("Endangered Animals of Thailand", 1990; "Popular Handbook of Indian Birds", 2007; Datta and Rawat, 2003; Datta, 1998; Kannan and James, 1999)

Great hornbills are fairly large, ranging from 95 to 120 cm in length and featuring a wingspan of 151 to 178 cm. On average, they weigh 3 kg. They are vividly colored and easily recognizable. The body, head, and wings are primarily black; the abdomen and neck are white. The tail is white and is crossed by a subterminal black band. A preen gland near the tail secretes tinted oil, which is spread across the feathers by the bird during grooming. This may give the bill, neck, casque, and tail and wing feathers coloration varying from yellow to red. The most recognizable feature of hornbills is the casque, which is a hollow structure located on top of the bill. It may be used by males to fight with other males and attract females. Like many other hornbills, these birds have prominent eyelashes.

Males and females are similar except that the irises of males are red while those of females are white, and males have slightly larger bills and casques.

The feature that distinguishes B. bicornis from other species is its greatly curved bill and prominent casque. ("Popular Handbook of Indian Birds", 2007; Golding and Williams, 1986; James and Kannan, 2009; Mobley, 2008; Raman, 1998)

Great hornbills breed between the months of February and May. Male casque size is important in attracting and fighting for mates. Males compete for females by butting into each other in the presence of a female prior to the breeding season. This could possibly be a display of superiority in competition for a mate. Mates, or potential mates, also perform duets where the male calls, the female replies, and they continue on in a loud volley. Buceros bicornis tends to be monogamous, and the pair remains together throughout their lives. (Raman, 1998; Golding and Williams, 1986; Mobley, 2008; Raman, 1998)

A unique feature of Buceros bicornis and some other hornbill species such as Buceros rhinoceros is the way that the female incubates and cares for her eggs. During the breeding period, which lasts between February and May, a monogamous pair chooses a tree in which to lay the eggs. This tree is usually a very tall, old-growth tree and the same one is used every year if possible.

After finding a hole in the tree that is large enough, the female uses both her own feces and her mate's to cover the entrance from the inside, thus confining herself inside. She makes a small slit through which the male provides food. In captivity, B. bicornis may use soft fruits such as bananas in addition to feces to cover the hole. While inside the hole, the female lays and then incubates on average two eggs. The male provides fruits from trees in the genus Beilschmiedia, which are widely available during the breeding season; she receives no nutrients other than this. In other hornbill species such as Buceros hydrocorax, other non-breeding birds in addition to the male may provide assistance by bringing fruit to a female incubating her eggs. The incubation period usually lasts between 38 and 40 days. Protected within the tree, the female completes a full molt which renders her flightless for a period of time.

After the chicks hatch, the female remains confined in the tree for around five weeks when she emerges to help the male gather food for the growing young. The young re-seal themselves within the cavity after the female leaves. For the next two weeks, the both parents provide food for the young. After the young emerge, the parents continue to feed them until they reach roughly 15 weeks of age, at which point they are considered independent. (Choy, 1980; Datta and Rawat, 2003; Golding and Williams, 1986; James and Kannan, 2007; Mobley, 2008; Poulsen, 1970)

Parental investment in this species consists of providing food for young throughout the time period between hatching and independence. The mother is confined within the nest tree for a few weeks during the pre-hatching period, which usually lasts a few weeks, and for approximately five weeks after hatching.

During these periods, the male provides food while the female and young are protected in the tree. The male must forage extensively for lipid-rich fruits in order to feed himself as well as the female and the young. The male and female continue to feed the young throughout the pre-independence period until roughly fifteen weeks of age.

Great hornbills also invest energy in defending a nesting territory. They are only territorial during the breeding season, and may defend a 100 m area around the nest. (Datta and Rawat, 2003; Poulsen, 1970; Datta and Rawat, 2003; Golding and Williams, 1986; Poulsen, 1970)

Buceros bicornis may live up to fifty years of age in captivity, but range from 35 to 40 in the wild. Though B. bicornis may occasionally be hunted by man, they lack natural predators and their food is often plentiful. These two things allow for a relatively long lifespan. (Mobley, 2008)

Great hornbills tend to stay in small groups of monogamous pairs and their offspring. They are active during the day and at night they gather in large communal roosts which may contain hundreds of individuals. They are a non-migratory species but generally move within an area of 14.7 square kilometers. Males fight each other by butting their casques, possibly as a display of dominance in competition for females. One notable behavioral feature is the sealing up of the female in the nest tree during the breeding season. (Golding and Williams, 1986; Mobley, 2008; Poulsen, 1970; Raman, 1998; Golding and Williams, 1986; Mobley, 2008; Poulsen, 1970; Raman, 1998; Golding and Williams, 1986; Mobley, 2008; Poulsen, 1970; Raman, 1998; Golding and Williams, 1986; Mobley, 2008; Poulsen, 1970; Raman, 1998; Golding and Williams, 1986; Mobley, 2008; Poulsen, 1970; Raman, 1998; Golding and Williams, 1986; Mobley, 2008; Poulsen, 1970; Raman, 1998; Golding and Williams, 1986; Mobley, 2008; Poulsen, 1970; Raman, 1998)

The home range of Buceros bicornis varies from less than four square kilometers during the breeding season to nearly fifteen square kilometers during the non-breeding season. (Poonswad and Tsuji, 2008; Poonswad and Tsuji, 2008; Poonswad and Tsuji, 2008; Poonswad and Tsuji, 2008)

Except for the time during nesting season, Buceros bicornis vocalizes very loudly. The sounds they produce can be described as "cackling" or "roaring." Great hornbills are most vocal within large, communal night roosts. Roosts are often hypothesized to be "information hubs" where individuals can share information regarding good feeding sites, for example. Pairs of great hornbills use duets as part of courtship, where a male and female alternate calls to each other. The location of individuals can be identified by sound alone due to their vocalizations combined with the characteristic "whooshing" sound produced by their flight. This unique flight sound is produced from lack of flight feather coverts.

Male great hornbills use tactile forms of communication to compete for mates. Males collide bill casques, often in flight, during the time preceding the breeding season. The size of male bill casques also likely serves as visual communication to potential mates. Like all birds, great hornbills perceive their environments through visual, tactile, auditory and chemical stimuli. ("Endangered Animals of Thailand", 1990; "Popular Handbook of Indian Birds", 2007; James and Kannan, 2009; Mobley, 2008)

Members of this species are predominantly frugivores that feed on both lipid-rich and sugar-rich fruits but feed on small mammals, birds, amphibians, reptiles, and insects as well. The lipid-rich fruits include those in the genus Knema and Myristica commonly known as nutmeg trees, and several in the family Lauraceae such as Beilschmiedia. Though these lipid-rich fruits may be available throughout the year, they are particularly abundant during the breeding season. As a result, B. bicornis relies on these fruits as its primary source of energy during the breeding season when energy needs are significantly higher for both the parents and young. This is also true for other hornbill species in the same region, such as Malabar gray hornbills (Ocyceros griseus).

During the rest of the year, great hornbills rely on sugar-rich fruits such those of Vitex altissima and several species in the genus Ficus (fig trees). Figs account for the majority of fruit consumption of B. bicornis throughout the year. Great hornbills have been known to protect fig trees from other birds such as wreathed hornbills (Rhyticeros undulatus). (Datta and Rawat, 2003; Kannan and James, 1999)

Buceros bicornis has few if any natural predators due to its relatively large size and the fact that members of this species tend to occupy the canopy. However, humans occasionally hunt and kill great hornbills for their meat, casque, and feathers for subsistence, medicinal, or ritualistic purposes. ("The Status and Conservation of Hornbills in Cambodia", 2004; Azua and Czekala, 2003; Mobley, 2008)

Due to its large gape, Buceros bicornis is able to transport and disperse seeds of trees in the genus Myristica, which tend to be too large for other organisms. These trees rely on B. bicornis for seed dispersal since only a few other birds (such as Ocyceros griseus) are able to ingest the seeds intact to later disperse. They also impact populations of small mammals, birds, amphibians, reptiles and insects that they occasionally consume. (Kannan and James, 1999; Gale and Thongaree, 2006; Kannan and James, 1999; Raman and Mudappa, 2003)

Buceros bicornis is kept in zoos in various parts of the world. Efforts to breed this species in captivity are generally not successful.

The casque of B. bicornis is used as an ornamental piece by natives. They are also occasionally hunted for their meat and feathers for subsistence, ritualistic or medicinal purposes.

They are also an important seed disperser which aids in forest propagation. (Azua and Czekala, 2003; Choy, 1980)

There are no known adverse effects of Buceros bicornis on humans.

Buceros bicornis is considered "near threatened" on the IUCN Red List. The biggest threat to this species is habitat destruction, and particularly the removal of the old-growth trees that these birds require for nesting. Their large size and distinctive sounds make great hornbills relatively easy targets for hunters, who value them for their meat, feathers and casque, which is used for ornamental purposes among natives. They are listed under CITES appendix I which restricts trade of the species for exceptional purposes only. ("Endangered Animals of Thailand", 1990; Datta, 1998; James and Kannan, 2009; "Endangered Animals of Thailand", 1990; Datta, 1998; James and Kannan, 2009)