Hornbills are a group of birds (family Bucerotidae) distinguished by their large, down-curved bills. They are, in fact, the only birds in which the first and second neck vertebrae are fused to support the heavy bill. A hollow, horn-like structure called the casque lies on the upper mandible, a feature that gives hornbills their name. Their eyes are shielded by prominent lashes that provide shade from the sun.
Scientific Classification
Animalia
Chordata
Aves
Bucerotiformes
Bucerotidae
Scientific Classification
Animalia
Chordata
Aves
Bucerotiformes
Bucerotidae
These birds are found in tropical and subtropical regions of Africa, as well as in Asia and Melanesia. They are omnivores, consuming fruit, insects, and small vertebrates. Hornbills living in forests play an indispensable ecological role as seed dispersers.
In a unique reproductive strategy, female hornbills seal themselves inside a tree cavity when they are ready to lay eggs. This ensures that their newly hatched chicks are protected from predators.
Hornbill (Species and Types)
Species
According to the International Ornithologists’ Union, as of 2023, there are 62 species of hornbills. Given below is a list of the most common species based on their regional distribution.
Size: Body Length – Around 30 in (75 cm) on average
The smallest species, the red-billed dwarf hornbill, measures only about 12 in (30 cm), while the largest, the southern ground hornbill, is 35 to 39 in (90 to 100 cm) long.
Hornbill
Weight: 5 lb (2.3 kg)
The heaviest, the southern ground hornbill, weighs around 7.6 to 13.6 lb (3.5 to 6.2 kg), whereas the smallest, the red-billed dwarf hornbill females, weigh 2.9 to 4 oz (84 to 115 g).
Body and Coloration: These birds are characterized by their large, curved, brightly-colored bills. Along the upper mandible of the bill lies a notable hollow structure, the casque, which serves to reinforce the bill. However, in the helmeted hornbill, the casque is not hollow; instead, it is filled with hornbill ivory and is used for battering in aerial fights.
Depending on the species, the plumage of hornbills may be black, gray, brown, or even white. Some species, like the southern ground hornbill, have patches on their face and throat where feathers are absent. These patches are brightly colored and can become more vivid during the breeding season, signaling sexual receptivity.
Distribution
These birds are found in sub-Saharan Africa and Southeast Asia, extending to Melanesia. No genus exists in both Asia and Africa.
24 species are found in Africa, whereas 10 are found in the Indian subcontinent. Indonesia is home to 13 species, including 9 in Sumatra, while the remaining ones are distributed across Sumba, Sulawesi, Papua, and Kalimantan. The Philippines has 11 endemic species of hornbills.
Fossil records suggest that these birds once existed in North Africa and South Europe during the Neogene Period (around 23 to 2.58 million years ago).
Hornbill Bird
Hornbill Beak
Habitat
Most hornbill species found in Africa occupy open woodlands and savannahs, though a few, like the black-casqued hornbill, are found in forests. A few species, like the Abyssinian ground hornbill, inhabit arid to semi-arid regions with scattered trees.
All hornbills in Asia, except the Indian grey hornbill (which lives in open woodlands), inhabit dense forests. Some species, such as the great hornbill, occupy hill and montane forests.
Hornbill Habitat
Hornbill Flying
Diet
They are omnivorous birds that have a varied diet comprising fruit, insects, and small vertebrates, including rodents, lizards, frogs, and sometimes even small snakes. Some species, like the Malabar pied-hornbill, have a preference for the fruits of the strychnine tree (Strychnos nux-vomica).
Behavior
Hornbills are diurnal birds that forage in pairs or small groups in the morning. In between meals, they preen themselves. They also clean their bill and casque by rubbing them against tree branches or bark. At night, hornbills return to their home tree for roosting.
They emit a wide range of vocalizations, ranging from deep booming sounds to toots, bellows, and cackles. The booms of Southern ground hornbills are so loud that they are often mistaken for the roar of lions.
Hornbills use the tip of their bill to pluck fruits from trees or animals off the ground. However, they cannot swallow the captured food as their tongues are too short to manipulate it. Thus, they jerk their heads and toss the food back into their throats.
Lifespan
These birds typically live between 35 and 50 years in the wild. However, some species, like the southern ground hornbill, survive over 70 years in captivity.
Reproduction and Life Cycle
These birds typically form monogamous pairs. The males attempt to court the females by providing them with food throughout the year. Once selected by a female, the pair spends several days seeking the perfect tree cavity where they can build the nest. After spotting the cavity, they line it with leaves, feathers, and grass.
When the female is ready to lay eggs, she slips into the nest and gradually seals the opening with a mixture of mud, droppings, and fruit pulp. Only a slit remains, large enough for the male to transfer food. This nesting behavior effectively protects the eggs and chicks from predators.
After the nest is sealed, the female takes about 5 days to lay her first egg. Females of smaller species lay as many as eight eggs in a clutch, while those of larger species lay only one to two. The mother sits on the eggs and incubates them. During this incubation phase, she molts most of her wing and tail feathers, becoming incapable of flight for several weeks.
Hornbill Nest
Hornbill Chick
Since the eggs are laid days apart, the chicks hatch at different times. They are born naked and pink, with their eyes closed. When the chicks grow considerably in size, the mother breaks out of the nest and joins the father in tending to the chicks. Typically, the oldest chick survives, while the younger ones die of starvation.
The young bird fledges after 2 months but continues to stay with the parents. By the time it is 4 months old, it has already learned how to gather its food and is ready to move out independently.
Predators
Hornbill eggs and chicks are vulnerable to pythons, monitor lizards, and birds of prey, including eagles, owls, and large hawks. Some mammals, such as civets, genets, mongooses, and even baboons, have been found raiding hornbill nests.
Adult hornbills fall prey to leopards and raptors, like crowned and martial eagles.
Conservation Status
Although the populations of the African species of hornbills are relatively stable, those of the Asian species are affected by hunting and habitat loss. For instance, the Palawan and Visayan hornbills are categorized as Vulnerable (VU) in the IUCN Red List of Threatened Species. The Mindoro hornbill is Endangered (EN), while the rufous-headed hornbill and the Sulu hornbill are Critically Endangered (CR). In fact, the Sulu hornbill is one of the world’s rarest birds, with only 40 mature individuals remaining. The helmeted hornbill is also Critically Endangered (CR) due to the intense hunting pressure for its ivory.
