Class: Aves (Birds)
Body length: largest— southern ground hornbill Bucorvus leadbeateri, up to 33 inches (100 centimeters); smallest— red-billed dwarf hornbill Tockus camurus, 12 inches (30 centimeters)
Weight: southern ground hornbill males up to 13 pounds (6 kilograms); red-billed dwarf hornbill males up to 4 ounces (122 grams)
Life span: 35 to 40 years in the wild, up to 50 years in zoos
Incubation: 23 to 96 days, depending on species
Number of eggs laid: smaller species up to 7 eggs, larger species 1 to 2 eggs
Weight at hatch: 1 to 3 ounces (28 to 100 grams)
Age of maturity: smaller species reach maturity at 1 year, larger species at 3 to 6 years
Conservation status: Sulu hornbill Anthracoceros montani and Visayan wrinkled hornbill Aceros waldeni are at critical risk.
• Some hornbill species apply makeup! Their bills are
stained red-yellow and orange by preening oil from a gland
at the base of their tails.
• Southern ground hornbill booms are so loud they are sometimes mistaken for the roaring of lions!
• Often the first sign of an approaching hornbill is the rhythmic chuffing sound made by their wings as they fly through the air, which can be heard at long range.
• The weight of a hornbill's casque and bill are so heavy that the first two vertebrae in their necks are fused to support the weight.
• In 1972, the San Diego Zoo Safari Park received the Association of Zoos and Aquariums' Edward H. Bean Award for producing the first Abyssinian ground hornbill chick Bucorvus abyssinicus in a zoo. This pair lived to be more than 50 years old and produced 50 chicks!
I feel pretty
With long eyelashes, dark eyes, and an almost comically large, curved bill, hornbills have many admirers (the eyelashes are modified feathers!). These birds range from the size of a pigeon to large birds with a 6-foot (1.8-meter) wingspan. You can easily pick out a hornbill from other birds by a special body part atop their bill called a casque. Hornbills have a long tail, broad wings, and white and black, brown, or gray feathers. This contrasts with the brightly colored neck, face, bill, and casque in many species. Females and males will often have different colored faces and eyes. Their closest relatives are kingfishers, rollers, and bee-eaters.
Most hornbills are omnivorous and eat a combination of fruit, insects, and other small animals. The birds can use the tip of their bills as fingers to pluck fruit from trees or animals off of the ground. The edges of the bills are notched like a saw for grasping and tearing. The larger hornbill species tend to eat mostly fruit and travel from tree to tree in pairs or larges flocks.
There are two species of hornbill that are unique because they are carnivorous and spend most of their time on the ground: the Abyssinian (or northern) hornbill Bucorvus abyssinicus and the southern ground hornbill Bucorvus leadbeateri . These species patrol their territory on foot in groups of up to a dozen individuals. They will eat mice and other rodents, frogs, and even venomous snakes, which they catch by using their long bills as tongs to keep out of harm's way.
Hornbills at the San Diego Zoo and the San Diego Zoo Safari Park get a combination of fruit, yams, domestic cat and dog kibble, mice, crickets, and mealworms, with the carnivorous birds getting more meat items than the other species.
Task for a casque
In most hornbill species, the casque is a hollow or spongy structure made out of keratin. It is believed that this structure acts as a vibrating chamber to make the hornbill's voice louder. The calls made by the bird range from the deep booming sounds they make as they begin foraging to brays, toots, bellows, and cackles. The bill and casque of juvenile birds are underdeveloped, and females often have much smaller casques than males. This may be because males also use their casques to attract mates and display their health and strength to other males. The males of some species even compete by knocking their casques together in mid-flight.
The casque of the helmeted hornbill Rhinoplax vigil from Borneo is different from all other hornbill species: its dense, ivory-like casque makes up about 10 percent of the bird's body weight! Unfortunately, this has made it attractive to native islanders who kill the birds to use the heavy casques for ornamental carvings.
Hide and seek
Talk about a stay-at-home mom: the female hornbill will seal herself up in the hollow of a tree for up to four months while raising her chicks! But first, the hornbill pair will perform a courtship ritual that may include preening, feeding, wing and tail displays, and even beating their bills on the ground. Then the pair will spend several days choosing just the right tree hollow to line with leaves, grass, and feathers. After breeding, the female will use regurgitated food, droppings, and mud brought to her by the male to seal the opening of the tree hollow until only a small slit remains. This creates an almost predator-proof nest!
The female will lay her eggs and sit on them while the male flies back and forth bringing her whole or regurgitated food, which he feeds to her through the slit. The female keeps the nest clean by dropping all waste outside through the small opening. In some species, the female will molt most of her wing and tail feathers at this time, leaving her unable to fly for several weeks. In other species, the female will break out of the hollow when the chicks are half grown; the chicks will reseal themselves in the nest and are fed by both parents until they are ready to fledge.
Ground hornbills Bucorvus sp. are the exception to this style of chick rearing. They do not seal the entrance to their nest and both male and female take turns incubating the eggs and tending to the chicks.
Friends of a feather
Hornbills have developed some interesting relationships with other animals. Eastern yellow-billed hornbills Tockus flavirostris work with dwarf mongooses to gather food! The mongooses will wait for the hornbills to arrive before setting out; if the hornbills arrive before the mongooses are up and about, the birds call down the burrow to them. The hornbills benefit by eating all the insects stirred up by the foraging mongooses, and the mongooses gain extra eyes and ears to look out for danger.
The smallest hornbill, the red-billed dwarf hornbill Tockus camurus follows squirrels and swarms of driver ants to snatch up the insects that are disturbed. Even elephants in Africa and bears in Asia play a part in a hornbill's life by knocking down tree branches and creating perfect hollows for nesting sites.
Help the hornbills
Despite their quirky and comical nature, hornbills are in trouble. Habitat destruction and hunting are the biggest threats to hornbills, and it is believed that there are only 120 pairs of Visayan wrinkled hornbills Aceros waldeni and fewer than 20 pairs of the Sulu hornbills Anthracoceros montari. The Sulu hornbill's tiny population is limited to one island in the Philippines (Tawitawi), and military activity makes conservation difficult. Other threats for hornbills include introduced species such as feral goats, which are preventing forest regeneration by eating new growth.
Some hornbill species are in danger of becoming target practice for hunters or being captured for the exotic pet trade. Many hornbills are killed for their casques, which are used for carvings and traditional medicines. In Sarawak, Malaysia, local people were hunting hornbills for the feathers, which are used for headdresses and ceremonies. Then the Wildlife Conservation Society came up with a plan: they asked ceremonial leaders and dancers if they'd be willing to use donated feathers so they wouldn't have to kill so many native hornbills. The leaders said yes! Now, zoos with hornbill collections, including San Diego Zoo Global, collect their hornbills' shed feathers for regular shipments to Sarawak.
San Diego Zoo Global has the most comprehensive collection of hornbills in the United States at nearly 30 species. We have hatched more than 520 hornbill chicks, which is among the highest number of hornbill hatchings in the world. Hornbills are symbols of luck, purity, and fidelity in many cultures, and this may help the hornbill's human neighbors join in the fight to conserve these fabulous birds.