HORNBILLS: BucerotidaeSOUTHERN GROUND-HORNBILL (Bucorvus leadbeateri): SPECIES ACCOUNTS
HELMETED HORNBILL (Rhinoplax vigil): SPECIES ACCOUNTS
SULAWESI RED-KNOBBED HORNBILL (Aceros cassidix): SPECIES ACCOUNTS
Hornbills are medium- to large-sized, stocky, and highly vocal birds that are described as flamboyant, very showy. They have long, oversized but lightweight, slightly decurved (down-curved) bills. The bills are located below noticeable casques (KASKS), horny growths. The casques come in various sizes; shapes, including bumps, ridges, or horns; and colors such as brilliant orange, yellow-gold, deep crimson, or shiny black. Experts think casques might be used to help support large bills, make calls louder, or attract mates.
Hornbills have patches of bare skin around the eyes and throat and long eyelashes on their upper lids. To support their head and large bill, they have strong neck muscles and two neck vertebrae, bones in the spinal column, connected together. Hornbill plumage, feathers, is not very colorful, usually with areas of black, white, gray, or brown. The color and size of plumage and the shape of the casque identifies the age and sex. Hornbills vary in size and shape, from 11.8 to 47.3 inches (30 to 120 centimeters) long, and weigh between 3.5 ounces and 13.25 pounds (100 grams and 6 kilograms). Males are larger and heavier than females and have bills that are up to 30 percent longer.
Hornbills are found in sub-Saharan Africa; from India and continuing east through south and Southeast Asia; onto the Indonesian and Philippine archipelagos including New Guinea; and east to the Solomon Islands.
Hornbills inhabit deserts, rainforests, steppes (treeless plain, often semiarid and grass-covered), woodlands, savannas (flat grasslands), and mountains, but prefer forested areas to other locales. Hornbills must be near large trees in order to nest and feed. Different species prefer various habitats, allowing many species to live in the same area.
Hornbills eat a variety of food, from animals to fruits and seeds. They are omnivorous, eating both meat and fruit in their meals.
BEHAVIOR AND REPRODUCTION
Hornbills generally groom their feathers as their first activity after dawn, and then begin searching for food. They move in pairs, but some species move in family groups of three to twenty. When plenty of food is available, larger groups may come together. Bills are used for various functions including feeding, grooming, and nest-sealing. They are not considered as migratory birds, but are territorial for many species.
Hornbills display sounds that are described as the noise made by an approaching train. The sound is possible because hornbills do not have small feathers that cover their flight feathers; so wings allow air to pass through, producing train-like vibration sounds. These "whooshing" sounds come in different intensities depending on wing size, and are used to defend the territory and to maintain contact with group members.
Hornbills are believed to be monogamous (muh-NAH-guh-mus), having only one mate. Usually one breeding pair will be joined by earlier offspring who help raise the latest brood. Courtship begins when pairs fly together through the air, perch close to each other, groom one another, and exchange food.
Hornbills use an interesting nesting pattern. They build nests in holes, mostly natural cavities, hollow areas, in trees or rock crevices. However, unlike most other birds, all hornbills, except a few, seal the cavity entrance, leaving only a slit through which the female, and later her young, receive food from the male. The male brings mud to the female who use it, along with her saliva, to seal the opening. If mud is not available, the female will substitute her own feces, solid waste. Egg size and number, and incubation period, the time needed to sit and hatch the eggs, depends on female body size. Clutch size, number of eggs hatched together, ranges from two to three eggs in large hornbills, and up to eight for smaller hornbills. Incubation periods run between twenty-three and forty-nine days. Eggs hatch in intervals, with the chicks emerging naked, pink, and blind. Feather growth begins in a few days, with the skin turning black. Fledglings, young who have grown enough feathers to be able to fly, have underdeveloped casques and small bills, but after about one year, their appearance is like the adults.
HORNBILLS AND PEOPLE
People hunt hornbills for food and as a treatment for ailments. The birds play an important role in the customs and traditions of local people. Their feathers, heads, and casques are valued. They are often adopted as local mascots or state birds.
Two hornbill species are Critically Endangered, facing an extremely high risk of extinction in the wild. Two species are Endangered, facing a very high risk of extinction in the wild. Five species are Vulnerable, facing a high risk of extinction in the wild, and twelve species are Near Threatened, may become threatened with extinction.
Physical characteristics: Southern ground-hornbills are the largest in size and darkest in color of hornbill species. They are black with white primary feathers, the largest flight feathers, and red throat skin. Males have bare facial skin, and throat skin that can expand. Females have a blue patch on their red throat skin. When flying, white wing patches are visible. Juveniles are browner than adults, with black flecks in the primary wings, gray sides that reach to the bill, and pale gray-brown facial skin. Adults are 35.4 to 39.4 inches (90 to 100 centimeters) long. The male weighs between 7.6 and 13.6 pounds (3.5 and 6.2 kilograms) and the female weighs between 4.9 and 10.1 pounds (2.2 and 4.6 kilograms).
Geographic range: They are found in eastern South Africa, Botswana, northern Namibia, Angola, and southern Burundi and Kenya.
Habitat: Southern ground-hornbills live in woodlands, savannas, and grasslands next to forests. They are found at elevations up to 9,800 feet (3,000 meters), preferring moist habitats.
Diet: Southern ground-hornbills are mostly carnivorous, eating only meat. They eat insects, grasshoppers, beetles, scorpions, and termites. During the dry season, they also eat insect larvae (LAR-vee), snails, frogs, and toads. Sometimes southern ground-hornbills eat larger prey, such as snakes, lizards, rats, hares, squirrels, and tortoises. At times, they will eat carrion (decaying animals), fruits, and seeds. The birds are able to eat these animals by using their powerful dagger-like bills to cut and tear their prey. Southern ground-hornbills hunt in groups from the ground by walking, probing, pecking, and digging.
Behavior and reproduction: Southern ground-hornbills roost in trees. They live in groups of up to eight birds, with each bird of the group sharing and defending a territory. The territory may be as large as 36 square miles (100 square kilometers). Nests are holes in trees or rock faces, lined with dry leaves brought by males. The entrance is not sealed. Females lay one to three eggs at intervals of three to five days, usually from September to December. The incubation period is thirty-seven to forty-three days. Adult and immature helpers usually assist the dominant pair, and feed the nesting female. Chicks are hatched with pink skin that turns black within three days. At about eighty-six days, young birds fledge, or grow the feathers necessary for flight. Southern ground-hornbills remain with the parents at least until maturity, about four to six years.
Southern ground-hornbills and people: Local people think highly of southern ground-hornbills, but also eat them for food and medicinal, healing, purposes.
Conservation status: Southern ground-hornbills are not threatened. They are widespread and common throughout their geographic range except in some areas of South Africa and Zimbabwe where their populations are declining. ∎
Physical characteristics: Helmeted hornbills are large, dark brown and white birds with short red bills. They have high, nearly solid, heavy casques, and long, white tail feathers. Adults are 37.4 to 41.4 inches (110 to 120 centimeters) long, with females weighing between 5.7 and 6.3 pounds (2.6 and 2.8 kilograms) and males weighing about 6.7 pounds (3.1 kilograms).
Geographic range: Helmeted hornbills are found in South Myanmar and south Thailand, Malaysia, Sumatra, and Borneo.
Habitat: They prefer rainforests primarily at a habitat below an altitude of 4,900 feet (1,500 meters).
Diet: Helmeted hornbills eat many different types of figs.
Behavior and reproduction: They are believed to be territorial. The species has a distinctive loud call that includes a series of introductory "tok," followed by a flowing laughter-like sound. Both sexes regularly engage in strange, aerial hammering and head-butting behaviors with the use of their casque, especially near fruiting fig trees.
Little is known about the reproduction of helmeted hornbills. Females breed throughout the year, but in southern Sumatra, fledglings are usually found between May and June.
Helmeted hornbills and people: People in Southeast Asian cultures consider the helmeted hornbill to be one of their most significant species. They are widely hunted for their feathers and casques ("ivory") that are valued for traditional dances and ceremonial decoration. Illegal carved casques are still traded internationally.
Conservation status: Helmeted hornbills are considered Near Threatened and listed on Appendix I of the Convention in International Trade in Endangered Species (CITES). They are common where its range is left undisturbed. However populations are declining throughout most of its range due to hunting and forest destruction. ∎
Physical characteristics: Sulawesi red-knobbed hornbills are black with a white tail. They have a high, wrinkled, red casque. Necks are rufous, reddish, in males, and black in females. Their beaks are ridged and yellow with blue throat skin. Adults are 27.6 to 31.5 inches (70 to 80 centimeters) long. Female weight is unknown, and male weight is between 5.2 and 5.5 pounds (2.4 and 2.5 kilograms).
Geographic range: They are found in the Indonesian island of Sulawesi and nearby islands of Lembeh, Togian, Muna, and Buton.
Habitat: Sulawesi red-knobbed hornbills prefer lowland rainforests, particularly at altitudes below 3,600 feet (1,000 meters).
Diet: They eat a very wide range of fruits, mostly off of the top of the forest's canopy.
Behavior and reproduction: The Sulawesi red-knobbed hornbill is a non-territorial bird, that ranges across a wide area of land. They are usually seen in pairs, but also observed in large numbers, usually fewer than 120 individuals, while feeding at fruiting figs trees. They emit a loud barking call that can be heard for more than 1.2 miles (2 kilometers). Sulawesi red-knobbed hornbills assist in the scattering of seeds and growth of plants because they eat many fruits.
Nesting begins in June or July, at the end of the rainy season so young can feed during the fruit season. Nests may be built near others, often up to ten mating pairs per 0.4 square miles (1 square kilometer). Females usually lay two to three eggs, with an incubation period of between thirty-two and thirty-five days and nestling period of about 100 days.
Sulawesi red-knobbed hornbills and people: People believe that the feathers and casques of Sulawesi red-knobbed hornbills are filled with powers that give the owner protection from all types of problems. Their feathers and casques are, therefore, used to decorate headdresses and drums for traditional warrior dances. Their meat is also eaten by people.
Conservation status: Sulawesi red-knobbed hornbills are not threatened. They are locally found with densities of up to 130 birds per square mile (51 birds per square kilometer). Distribution is slowly becoming more restricted due to the decline in forested areas. ∎
FOR MORE INFORMATION
del Hoyo, Josep, et al., eds. Handbook of the Birds of the World. Barcelona: Lynx Edicions, 1992.
Dickinson, Edward C., ed. The Howard and Moore Complete Checklist of the Birds of the World, 3rd ed. Princeton, NJ and Oxford, U.K.: Princeton University Press, 2003.
Fry, C. Hilary, and Kathie Fry. Kingfishers, Bee-Eaters and Rollers: A Handbook. Princeton, NJ: Princeton University Press, 1992.
Harrison, Colin James Oliver. Birds of the World. London and New York: Dorling Kindersley, 1993.
Forshaw, Joseph, ed. Encyclopedia of Birds, 2nd ed. San Diego, CA: Academic Press, 1998.
Perrins, Christopher M., and Alex L. A. Middleton, eds. The Encyclopedia of Birds. New York: Facts on File, 1985.
Stattersfield, Allison, J., and David R. Capper, eds. Threatened Birds of the World: The Official Source for Birds on the IUCN Red List. Cambridge, U.K.: BirdLife International, 2000.