HORNBILLS, THEIR NEST-BUILDING BEHAVIOR AND SPECIES IN ASIA

HORNBILLS


Hornbills are a kind of bird named after their the large horn-like bills found on most species. . There are 54 species of hornbill: 23 species living in the savannahs and forest of Africa and 31 species in Asia, living mostly in tropical rain forests. Only four species are found east of the Wallace Line. [Source: Michael Long, National Geographic, July 1999]

Hornbills first appeared in the fossil record about 15 million years ago. They are found in many myths of tribes on Southeast Asia and Indonesia. Borneo hill tribes regard rhinoceros hornbills as deliver of souls to the afterlife. In western Borneo, a celebration honoring hornbills is held every five to seven years. On Sumba, they are symbols of fidelity.

Hornbills are found only in the Old World. Toucans are regarded as their New World equivalent. The largest hornbill are the size of turkeys. The smallest is the size of doves. Many large ones have horn-like casques on their bill. Some bird live as long as 45 years.

Many hornbills are endangered or threatened as a result of deforestation, loss of habitat and hunting for their bills, feathers and meat. Some have fallen prey to poisons left out for other animals. Other are taken by poachers who can sell the chicks of arre species of up to $1,000 a piece.

Hornbill Characteristics

Hornbill have long curving bills that are mostly yellow and can reach lengths of 13 inches. The bill is an integral part if the hornbill’s skull and is used by the bird to feed, fight, preen, make nests and keep snakes from attacking the vulnerable parts of their body. Bill development is often an indicator of sex and age.


The casque seems to serve primarily as a reinforcing ridge along the top of the bill. But may also play a role is sexual selection and amplify the bird’s calls. In many species it has been modified into a hollow resonator. The casque of helmeted hornbill it is a block of solid ivory and helps make the skull 11 percent of its body weight. The shape of the casque is often the easiest way to determine species.

Hornbills have strong neck muscles that support the head and two fused vertebrae in the neck, a feature unique among birds. These features stiffen and strengthen the neck, give power to the bill and turn the head into a kind of pick axe

Hornbills have bare facial skin and long eyelashes. Their eyes are often brightly colors with greens, reds, yellows and blues. The throat skin may form wattles, or inflation sacs. They have strong claws which allow then to grip the sides of trees like woodpeckers.

The feathers of hornbills or mostly black, gray or brown. Some species have white feathers that give them distinctive markings. Some species have long tail feathers. The loud whooshing noise emanating from some large hornbills as they fly is produced by gaps in the hornbill’s wing feathers and air being compressed in these gaps. Large hornbills lack feather that allow for smooth air flow. The wing beats of some species can be heard a half mile away.

Hornbill Behavior


Most hornbills are sedentary and live in defined territories. All the species save one that live in Africa live in savannahs and grasslands. Most of those that live in Asia dwell in the forests. Sometimes the forest dwellers fly beyond their territories to search for fruit. Sometimes the savannah dwellers migrate during the wet and dry seasons.

Hornbills make loud calls. Each species has its own distinctive calls. Helmeted hornbills of Malaysia produce noises that sound like hooting and laughter. The great Indian hornbill roars. Von der Decken’s hornbills clucks. Some species produce exaggerated displays while calling. The largest hornbill, the five-kilogram south ground hornbill, produces a booming deep bass call that can be heard 2½ miles away.

Hornbills are generally monogamous. Many mate for life. On the Indonesian island of Sumba, they are symbols of fidelity. Pairs usually share and defend a territory that ranges in size from 10 hectares to 100 square kilometers. Copulation usually tales place during the last phase of nest building. A few species form groups whose goals are to defend the group territory and help a dominant pair breed.

Males are slightly larger than females but females are more courageous, choosing to fight monitor lizards and snakes that males back off from.

Hornbill Feeding


seeds dispersed by hornbills

Hornbills primarily feed on fruit, figs and insects. Many species collect fruit in their neck pouch and hide them in caches. Some have to ability to clasp fruit, insects and other food with the tip of their bill and deftly toss it in the air and catch it their gullet like a person catching a piece of popcorn in their mouth. As a rule hornbills don’t drink. They get all the water need from their food. Only four species have ever been observed drinking.

Hornbills are important for seed dispersal and help spread the food they eat. They spit out the seeds of some fruit. Fig seeds are dispersed in their droppings.

In Africa, there are some ground species of hornbill that methodically search through their territories for living animals such as large insects, snakes and frogs.

Hornbill Nests


All but two species of hornbills nest in tree cavities or rock crevasses that are sealed shut except for a narrow, vertical slit. In places were there are shortages of tree cavities hornbills often fight among themselves and evict other birds or even snakes or large monitor lizards to gain access to a cavity.

The female is sealed inside. The slit is about a half inch wide: wide enough to pass food through but narrow enough to seal out potential predators such monkeys raptors and other predators that feed on eggs and young birds. If a snake tries to slither the female inside can fight it off with her bill. The sealed nests also act as a chastity belt.

Most nests are built in tree hollows. A typical one began as a hole pecked by a woodpecker that is enlarged by fungus. Later a bee colony moves in and the hole becomes larger after a bear scrapes it with his claws to gets honey from the bee’s nest.

David Attenborough wrote in The Life of Birds, "The female hornbill is very fussy about the nesting accommodation. To suit her, a tree hole has to be reasonably spacious. It must also have a chimney at the top that will serve as a bolt hole if attacked. Once she has selected it, she invariably improves it by plastering over any crevices or smaller holes. The material she uses varies according to her species."

After the females has made herself comfortable in a good nesting site the male brings lumps of soil moistened with his saliva and sometimes augmented with droppings, chewed wood and bark and other detritus. Together they build a wall of mud: he from the outside and she from the inside. The soil is applied with the side of the mouth. Among some species, the male swallows mud and regurgitates it in little balls to the female.

First subsidiary entrances are sealed, then the main one is changed into a slit. Much of the work is done by the female. While she is doing this the male brings her food as well as more material for the plastering. Once the wall is complete the female is trapped inside the nest with only a small hole to outside through which to get food and communicate.

Life Inside a Hornbill Nest


The female of small species lay up to six eggs and incubates them for 25 days. The females of large species lays two eggs and incubates them for 45 days. During this time and after the chicks are born the male is responsible for supplying food. After the chicks have hatched the male may make as many as 70 feeding trips a day, bringing the female and the chicks geckos, seeds, insects, frogs slugs, berries and occasionally snakes. The males of some large forest species swallow fruits and regurgitate them one at a time to the female.

The female ejects her excrement out the opening. She does this by putting her rear end to the hole and shooting her excrement as far as possible. This is done not only to keep the nest clean, reducing the chance of disease, but also to prevent predators from locating the nest by the smell of the excrement. In most cases it takes the chicks a while to master this technique and before they do the female picks up the excrement and toss it out the slot or uses it make repairs on the wall.

Female hornbills remain trapped inside the nest for three to five months, while their eggs are incubating and the chicks grow up. They molt while in the nest, casting out their flight feather shortly before laying the eggs and regrow them before emerging from the nest.

During their time in the nesting, the female and her young are totally dependent on the male for food. If something happens to him, often the whole family perishes. Among species that form nesting groups, the entire group gathers food for the nesting female. Among some African species, when the young chicks grow to a large size the female turns her nest into a split level with the upstairs for her and the downstairs for her chicks.

Hornbill Young Leave Their Nest

The period of confinement for the chicks ranges from around 50 to 90 days. The females of some species breaks out before the chicks fledge to help the male bring back food. Others break out when the chicks fledge. Sometimes the chicks help break down the wall two weeks to a month after the eggs hatch so the female can escape and then help rebuild the wall. In this case, both the female and male work full time collecting food for the chicks which grow up quick and get bigger and hungrier everyday.

When hornbill chicks are 45 to 80 days old their voice changes and parents respond by not bringing food. This encourages the chicks to break out of their walled nest. Typically they break a hole in the wall first and poke their head out and scan the outside world for the first time. It often takes a couple days for it get enough courage to leave. It has fly to leave.

When the chicks are ready to fly they break through wall while its parents squawk loudly in encouragement. Sometime simply getting out takes some effort because by this time the chicks have grown quite large. Often the maneuver one wing out first and pop out and land on branch. Later, with more encouragement from their parents and a little tough-love prodding, they learn to fly.

Large Asian Hornbills


Great hornbill

Some Asian hornbills are very large birds with magnificent bright red, yellow, blue and pink colorations. The rhinoceros hornbill is the largest of the 50 fruit-eating bird species and seven hornbill species found on Borneo. They reach a meter in length and are associated with the god of war by Borneo’s Iban people. They are huge birds whose wing whooshing noises bring to mind pterodactyls. Females use resin for plastering over the crevices and small holes in her nest hole.

The great Indian hornbill feed in fruit, primarily figs, plucked from among the foliage. In some cases the descend to the ground to gather fallen fruit. They live in small groups that roost communally. These birds generally spend their day methodically visiting one fruiting tree after another.

Helmeted hornbills have unique solid ivory casques and tail feathers that are over a meter long. They have been observed engaging n long bouts in which they repeatedly knock their heads together. They have one of the loudest calls, a deep hou hou.

Great Pied Hornbills


Great pied hornbills have a wing span of five feet and produce a loud huffing noise when they fly. They have yellow and white markings on their wings. Their yellow casque and bill has patches of red on it. To really look sharp the male applies a gloss of yellow oil to his bill and casque from a preen gland at the base of his tail. They live in rain forest and feed mostly on fruit but occasionally eat green snakes which they swallow like---a string of spaghetti.”

Males bring up to 13 meals of fruit a day to nesting females. One male was observed delivering 150 figs in one visit, regurgitated one after another, as well as beetles, snakes, giant scorpions, geckos, bats and young of other birds. They females reportedly like some variety to their diet and have refused food if they are brought to much of the same thing.

Great pied hornbills do not welcome human intrusions. They have been known to drop branches on scientists that observed their nesting habits without using a blind.

Rufuous-Necked Hornbills and Palawan Hornbills


Rufuous-Necked Hornbill

The rufuous-necked hornbill is 90 to 100 centimeters long. Males weigh 2.5 kilograms and females weigh 2.3 kilograms. The male is a colorful bird with dark wings, orange body, red flaps under its bill and blue splotches around its eyes. The female is all black. [Source: Canon advertisement in 2001 National Geographic]

The rufuous-necked hornbill lives in dense evergreen and deciduous forests at 700 to 2000 meters from northeast India to Vietnam. Fewer than 1,000 of the birds live in Thailand, its last stronghold, mostly in remote mountainous areas. Number elsewhere are unknown. They are threatened by hunting by tribesmen and loss of habitat due to logging and agriculture.

The rufuous-necked hornbill mate for life and call to each other constantly when they search for fruit in the forest. While she raises her chicks, the female is sealed inside a tree 20 meters above the ground, for three months and relies while her mate brings her food.

The Palawan hornbill is 55 to 65 centimeters long (head and body length) and weighs 601 and 713 grams. Found only on the Philippine island of Palawan and two neighboring islands, it lives primarily in primary and secondary forests but also found in mangrove swamps and cultivated areas. There are estimated to be 2,500 to 10,000 of them. [Source: Canon advertisement in National Geographic]

The Palawan hornbill is a great asset to fruiting trees. It gathers fruits in a gular pouch, then processes and spits out the seeds where they able to thrive, away from the competing parent tree. Living in pairs or small groups, this hornbill nests in large trees and ranges from undergrowth to canopy. The bird is threatened by deforestation, poaching and the capture of eggs for pets or feed.

Wrinkled Hornbills


Sunda Wrinkled Hornbill

Wrinkled hornbills live in lowland primary forests in Malaysia, Sumatra and Borneo. Their head coloring is similar to but not as pronounced as that of red-knobbed hornbills. They are between 65 and 70 centimeters in length and weigh between 1.2 and 1.5 kilograms. The number of wrinkled hornbills is unknown. Their habitat has been reduced by logging.

Wrinkled hornbills fly through the forest canopy looking for fruiting trees. They follow an undulating flight path, making soft coughing noises with their throats and loud rushing noises with their flapping wings. They are monogamous and pairs raise their young together.

The Visayan wrinkled hornbill is 60 to 65 centimeters long (head and body length).Males weigh 1.1 to 1.2 kilograms. Females weigh 700 to 800 grams. Found only on the Philippines’ Visayan islands, it lives primarily in primary forests. The bird is presumed extinct on Guimaras and now only survives on the Western Visayas islands of Negros and Panay. There are estimated to be only 120 to 160 of them left. [Source: Canon advertisement in a 2004 National Geographic]

The Visayan wrinkled hornbill has bright yellow, orange and red markings on its head and bill and produces load calls that can be heard at great distances away. When the female is ready to lay eggs she and her mate use mud to wall-off their three-hole nest. While nesting she remains inside the walled-off nest, relying on the male to bring food. If something happens to him the whole family perishes. The species is threatened by poaching and loss of primary forest habitat.

Red-knobbed Hornbills

The colorful red-knobbed hornbills, found only on Suluwesi, are sometimes called "flying dogs" because they produce a loud barking noise that can be heard 300 yards away as well a variety of croaks, squawks and honks. Weighing up to five pounds (2.2 kilograms), they feed mainly on fig tree trees and help the figs by dispersing their seeds in the bird's dropping. At nesting time females seal themselves inside tree cavities with their dropping. [Source: Margaret Kinnaird, Natural History, January, 1996]

Red-knobbed hornbills are found in huge concentrations on Suluwesi's Tangkoko volcano, where the world's highest densities of hornbills have been recorded. Fig trees in the Tangkoko-DuaSudara Nature Reserve sometimes draw 200 hornbills. The huge concentration are the result of an abundance of figs that fruit year round. Red-knobbed hornbills eat 30 of the 40 or so kinds of figs that grow on the volcano.

Males have a large red nob and an oversized red bill. After chicks are born, the male take care of almost all the food collecting duties. Figs on the volcano vary from pea-size to plum size. The hornbill’s favorite is a large cherry red fig that they eat in vast quantities and males present to females as a courtship gesture. They also eat berries, wild mangos, nutmegs, and avocado-like drupes. The birds are currently threatened by loss of habitat, which is vulnerable to catastrophic drought, fires and volcanic eruptions.

Southern Ground Hornbills

Southern ground hornbills are the largest hornbills. Residing in southern Africa, they weigh up to five kilograms and are the size of turkeys. They have dark bodies, bright red skin folds around their heads and throats and long black bills. They are the most carnivorous of hornbill species. Their bills, gullets and throats are large enough to swallow a squirrel whole, head first; their neck muscles and strong enough to break open the shell of a tortoise.

Southern ground hornbills hang out in small groups and move in a line through grass, brush and bush, snatching up insects and occasional mouses and scorpions. For relief from the hot sun they keep their mouths open to help them ventilate and open their wings to expose pare patch of skin on their wings Although the can fly they prefer to scamper on the ground. Each group has a leader that shows its dominance by giving out or withholding food. Females can be identified by ther blue patch under their bill.

Southern ground hornbills have disappeared from 70 percent of their range in South Africa. Most of the loses are the result of habitat destruction but a number of birds have been killed by farmers because they had the obnoxious habit of breaking windows when attacked reflections of themselves. One park ranger told National Geographic that he knew of one farmer that lost 27 windows in one afternoon and said the birds returned three weeks later to “see if they had gotten rid of their antagonists.”

Michael Long wrote in National Geographic: “they have chutzpah. They are dignified, self-assured, confident, inquisitive if not meddling, and have a tendency to manipulate.” They “can waak up look you forthrightly in the eye.”

Image Sources: Wikimedia Commons

Text Sources: National Geographic, Natural History magazine, Smithsonian magazine, Wikipedia, New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, Top Secret Animal Attack Files website, The New Yorker, Time, Newsweek, Reuters, AP, AFP, The Economist, BBC, and various books and other publications.

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© 2008 Jeffrey Hays

Last updated November 2012

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