As part of a recent project I have been reading about the different species of hornbills in Arunachal Pradesh. These birds are characterized by their magnificent beaks and colourful plumage, with variations among the different species. Living right across the country in the arid city of Ahmedabad, far away from the verdant forests of Northeast India, it was a delightful surprise to spot a pair of hornbills amongst a cluster of trees amidst the concrete jungle. These were not the eye-catching ones but their less conspicuous cousins, the Indian grey hornbills.
Among all the hornbill species in India, the Indian grey hornbill is the most widely distributed and can be found across most parts of the subcontinent. Unlike the other forest-loving hornbills this species prefers dry plains, foothills, and open habitats. It can be seen in deciduous forests, orchards, thorny scrub jungles, gardens, and, as it did for me, even surprise with sightings in the middle of a busy city.
Hornbills belong to the family Bucerotidae, characterised by the casque or protuberance on their beaks. These birds are usually large, with a long and downward curving beak sporting an elaborate casque, and colourful bare skin around the head
The Indian grey hornbill (Ocyceros birostris) belongs to the genus Ocyceros, which literally means ‘pointed horn’. The species name birostris means ‘two beaks’. This hornbill has a long, curved ivory-coloured beak that blackish at the base, and has a sharp, narrow protruding casque. Male and female birds look very similar, though the female is slightly smaller and has a less prominent casque. These hornbills are also smaller than the other hornbill species, growing up to half a metre in length.
Unlike the other colourful hornbill species found in India, the Indian grey hornbill, as its name indicates, is not brightly coloured. Instead, it has an ashy, silvery-grey body, with long tail feathers that end in a band of white. Adults have red eyes and the skin around the eyes is grey, while juveniles have brown-orange eyes with reddish-orange skin around; and beautiful eyelashes.
The Indian grey hornbill is primarily an arboreal bird. It flies with a rapid beating of its wings followed by a short glide. The pale edges on the wings and tail, and its long central tail feathers are noticeable when it is in flight. As they fly they give a series of short “kek-kek-kek” calls, and when they perch on trees they make a high-pitched squealing sound. The birds are usually seen in pairs or small groups. They feed mainly in canopies, but descend to the ground only to dust bathe, pick up mud pellets to seal their nest cavity, to pick up fallen fruit, or to hunt insects or reptiles.
The birds are fruit lovers, with fleshy figs and berries topping their list. They also feed on jamun, ber and neem fruits. A fruiting ficus tree is a popular partying spot for small flocks of grey hornbills. This love for fruits makes these birds important seed dispersers. Their diet also includes insects, reptiles, frogs and mice which they actively hunt. Some even feed on poisonous animals such as scorpions and snakes.
It is this adaptability in diet, as compared with other hornbills that are specialist feeders, that has enabled the Indian grey hornbill to inhabit a variety of landscapes, even close to human habitation.
The fruit-eating habit of hornbills is an important contributor to seed dispersal. Seed dispersal is vital as it ensures the propagation of trees. It also enables the trees to occupy new areas, thereby increasing green cover.
Hornbills are among the very few birds that can feed on fruits with large seeds. They digest only the fleshy parts of fruits that they swallow and then regurgitate the seeds, spitting them out, or defecating the seeds intact. As the hornbill flies from tree to tree, or during the nesting season flies back and forth over long distances to search for and carry food for its mate, the regurgitated cleaned seeds are dropped far and wide, enabling them to grow into trees far from the original trees from which they originated.
Thus hornbills are important in keeping the forest alive. If we lose hornbills, many forest trees that depend on them to spread their seeds may eventually disappear from the forest too. Hornbills symbolise not only the health of a forest, but also a key to their continued survival.
All hornbills are cavity nesters. While they cannot build their own nests or dig cavities, they use existing holes in a variety of trees to make their nest. What makes all hornbills distinct is their unique nesting behaviour. The process begins during a month-long courtship when the male presents the female with food. As they embark on playful behaviour the pair also check out tree cavities to select their nesting site. Having done this, the two prepare the nest by cleaning it, creating the wall lining, and undertaking repair work. Once the nest is ready, the female prepares to confine herself in the nest while the male continues to prove his ability to provide for her needs by bringing food and nesting material. The female then seals the nest entrance with her own faeces, food and bark fragments, and mud pellets brought by the male. Only her beak protrudes out from the sealed nest. This helps to protect the eggs and chicks from predators. She lays her clutch of between two and five eggs and incubates them for over 20 days. Throughout this period the male diligently flies back and forth, feeding his mate through her protruding beak. While confined in the cavity the female moults all her feathers. The mother emerges from the nest shortly before the chicks themselves are ready to fly, and the chicks once again seal the nest from the inside, even as they continue to be fed. Now both the parents share in providing food and caring for the chicks. One of Nature’s many marvellous examples of nurturing the young.
This unique nesting habit of hornbills has also, in recent times, become a threat to the very existence of all species of hornbills. The fact that they use the same nests over the years makes it imperative to protect that their nesting trees, and the habitats where they grow. In the forests of northeast India the one of the biggest threats to these birds has been the destruction of this habitat by fragmentation, deforestation and clearance of forest regions for agriculture and dams.
As the forests are being denuded, the hornbills are losing not just places to nest and breed; the loss of native trees also affects their diet, posing a significant threat to their survival.
A unique community-based initiative to protect nesting trees of hornbills is the Hornbill Nest Adoption Programme spearheaded by the Nyishi tribe in the Pakke Tiger Reserve in Arunachal Pradesh. The tribe which traditionally hunted hornbills for their casque which were a symbol of their tribal identity have become active partners in protecting and conserving the hornbill nesting areas. The programme invites donors across the world to become ‘hornbill parents’ by adopting hornbill nests. The donations help pay salaries to the local community nest protectors who patrol the area, and ensure that the habitat continues to invite these birds. What an appropriate way to celebrate a bird that is, in its unique way, a diligent nest protector and parent.