Hail to the Hornbill!


BY kabrams

Photography by Ken Bohn

In some cultures, hornbills are sacred. They are seen as messengers between humans and the spirit world, thought to be harbingers of rain, and considered a symbol of strength and success. They are an important part of community rituals and ceremonies, and they are depicted in art and heraldry.

Whether it’s their prominent bills and crests, their colorful feathers and markings, their unique breeding strategy, or their noisy and active lifestyle, there is much about hornbills to inspire wonder, admiration, and respect.


Hornbill Habits

Hornbills are a varied bunch of birds, with 54 species found in Africa and Asia. Most are forest dwellers, living in the tree canopy and feasting on many types of fruit. These birds play an important role in their ecosystem: they’ve been called the “farmers of the forest,” because they disperse seeds from the fruit they eat far and wide, which allows new trees to grow. And hornbills can eat a lot of fruit—the larger species consume nearly 1.5 pounds a day, which is 20 to 30 percent of their body weight! Some tropical forest hornbill species feed exclusively on fruit, while others enjoy some insect and small animal protein in their diet, as well.

Like many forest-dwelling birds, hornbills have broad, rounded wings. They are noisy fliers, and because of the whooshing sound of their feathers, they are often heard before they are seen. Their wings aren’t the only thing that gives them away, though—they have a variety of loud calls they use to communicate with one another. The calls differ between the species, including whistles, raucous cackles, hooting and howling, and drawn-out roars that can be heard over long distances.

NORTHERN HEADER Like most hornbills, northern ground hornbills Bucorvus abyssinicus are monogamous and form bonded breeding pairs.

Like most hornbills, northern ground hornbills Bucorvus abyssinicus are monogamous and form bonded breeding pairs.

Among these already exceptional birds, two species are further exceptions: the southern and northern ground hornbills. They are the largest hornbills, with males weighing from 8 to 13 pounds and measuring over 3 feet in length, and they spend their time on the ground, stalking through the African savanna. While they can fly, unlike their forest relatives they prefer to walk, and they have the long, strong legs, shorter toes, and padded feet to do it.

The ground hornbills’ diet is quite different, as well: they are carnivores. They forage in the grass and vegetation, grabbing up animal prey like insects, snails, spiders, lizards, snakes, tortoises, and sometimes even squirrels and hares. They use their heavy, sharp bill to catch and kill their meal, and then use the forceps-like bill tips to toss the prey up and into their mouth—the “throw and gulp” method.


The Horn on Their Head

It’s hard to miss it: the hornbill’s most distinctive feature is its large, curved beak and the ridge or crest that adorns it, known as a casque. It’s what these birds are named for, including the family name, Buceros, meaning “cow horn.” The casque runs along the top of the bill and often extends onto the skull. It is made of bony material covered in layers of keratin, which in some species form huge cylinders or impressive high crests that are mostly hollow but supported by a network of bony struts inside. One species takes that to the extreme: the helmeted hornbill’s casque is a solid block, about 10 percent of the bird’s weight, and males use it in bouts of aerial jousting, head-butting one another in flight to see which is more dominant. For most species, though, the casque seems to serve as a social signal and sign of maturity, and it is usually larger in males than in females.

As distinctive as the casque is, the bill itself is a versatile tool that the birds use for picking fruit or capturing prey—including small items like tiny figs or insects, which require dexterous manipulation—digging in leaf litter, bark, or soil; gathering nesting material; and preening their feathers. The bill is often marked with furrows, grooves, and serrations, and some are brightly colored. In fact, that’s another hornbill oddity: several species have a gland at the base of the tail that secretes colored oils, and as they preen, the color is transferred to and absorbed into the bill.


Time to Mud Up!

When it comes to nesting and raising chicks, hornbills once again prove to be exceptional. Most species are monogamous, and bonded pairs defend their selected territory. During breeding season, the pair chooses an open cavity in a tree or cliff face, and they line it with a deep layer of nesting material. So far, pretty typical bird behavior. But then there’s the hornbill twist: they use a pungent mixture of mud, feces, and smashed food to create a plaster to close up the opening to the nest. When there’s just enough room for the female to get through, she enters the chamber for her confinement, which in some species can last up to five months.

Once inside, the female finishes closing up the entrance until there is just a slit large enough for the male to pass food in to her. In the safety and security of the chamber, she lays her eggs—one or two for larger species, up to eight for smaller ones—incubates them, and raises the surviving offspring until they are ready to fledge. All the while, her loyal mate hunts for and brings her food, occasionally takes out soiled nesting material, and defends the nest site from any potential threats. For some species this is a family affair: they practice cooperative breeding, and the pair’s grown chicks from previous years help prepare the nest and provide food to their mother and new siblings. The only species that don’t “mud up” their nests are the African ground hornbills. All told, it’s a complex but effective strategy—one used only by these extraordinary birds!


In Need of Protection

It is estimated that there are only about 1,500 southern ground hornbills left in South Africa.

Recent confiscations have found as many as 250 helmeted hornbill bills and casques hidden in one individual’s luggage.

Unfortunately, the unique characteristics of these striking birds have placed them in jeopardy. They are large, territorial birds that require appropriate foraging and nesting sites, and they have slow reproductive rates. Habitat loss and fragmentation caused by timber extraction, forest conversion to agriculture, and human development is affecting species throughout their ranges. In some places, they are hunted for food, for their feathers used in traditional ceremonies, or for the illegal wildlife trade. Even the mighty African ground hornbills are under pressure: it is estimated that there are only about 1,500 southern ground hornbills left in South Africa.

The helmeted hornbill, in particular, is being decimated by wildlife trafficking. Its solid casque has been used for centuries as “hornbill ivory,” carved into figures and jewelry. Traditionally, the material was held in high regard and was known as “golden jade.” Recently, the demand for their casques has significantly increased; as rhinos and elephants are disappearing, traffickers are turning to other species, like the hornbills, for this type of material. Now, hunters are combing the forests killing as many helmeted hornbills as they can find. The bills and casques are then smuggled on the black market—recent confiscations have found as many as 250 helmeted hornbill bills and casques hidden in one individual’s luggage.

Southern Sulawesi hornbill Penelopides exarhatus sanfordi

But hornbills also have dedicated protectors, and there is increasing awareness of their plight. Government and legal agencies are apprehending wildlife traffickers, wildlife conservation organizations are spreading the word about saving hornbills through community education campaigns, and zoos are providing breeding and population management expertise. San Diego Zoo Global is partnering with the Mabula Ground Hornbill Project in South Africa for just such an effort. Our animal care personnel have worked with their staff on egg incubation and chick-rearing techniques to help increase the southern ground hornbill population, and we have provided tracking and photography equipment to enable researchers to keep an eye on birds once they have been introduced into the wild.

San Diego Zoo Global also supports the Thailand Hornbill Project and their “Adopt a Hornbill” program, in which organizations and individuals can donate funds to protect a family of hornbills in the wild. The funds provide an income to local people who watch out for the hornbills, as well as supporting students who are conducting research on the biology and ecology of hornbills in the area. Bringing back the reverence and respect these remarkable birds have inspired for thousands of years will ensure that they are appreciated well into the future. All hail the extraordinary hornbill!