Instead of building a nest like other big birds, great hornbills look for ready-made tree cavities. Finding one large enough to accommodate an adult female, which is about the size of a peacock without its train, and a chick or two isn’t easy. Once they locate a suitable opening, the female hornbills then do something bizarre. They enter the hole, and aided by their mates, seal the entrance using their droppings until only a slit is left through which their mates feed them. By necessity, such holes are in huge trees, which can collapse in storms or be logged. A nesting tree is precious real estate, and hollows are reused every year.
In the Anamalai Tiger Reserve, Tamil Nadu, great hornbills have been using five nesting holes since at least 1991. They don’t rear their young only in the forest. They also settle for cavities in large trees shading coffee in the adjoining plantations in the Valparai plateau. Since estates have fewer trees, do the males get enough fruit to feed their mates and later their ravenous progeny?
Locking beaks
Pooja Pawar, a student of wildlife biology, studied the hornbills in the two neighbouring habitats of forests and coffee plantations. If locating an appropriate tree hole was a challenge for hornbills, finding their nests was a bigger one for Pawar. A month before nesting began, usually in December, up to 50 birds gathered in the branches of roosting trees to find mates. Pawar hid below one such tree well before dawn. Rival males flew into the air, locked beaks and swirled down for less than half a minute in a competitive bout called casque butting. They played chicken in the air: the first to let go was the loser. Males that held their nerve in these acrobatics flew off with their chosen partners.
By following these pairs over several days, Pawar found their nests. This is when she realised why no one else had conducted such a study.
“Hornbills fly across a hill in 30 seconds,” she says. “It took me a whole day to cover that distance.”
She scouted 17 nests, but she couldn’t observe them all. Although she lay on the ground in the forest covered by a camouflage sheet while it was still dark, one nervous male refused to visit his mate as long as the researcher stayed. When this stand-off lasted five hours, she felt guilty and abandoned her vigil. Rather than forcing the female to go hungry, Pawar didn’t include it in her study.
Vetoed project
Another candidate nest was by a stream. She made the mistake of constructing a hide at the base of a fruit-laden jack tree. She didn’t see the elephants until they were so close that all she saw was a moving wall of grey. The limited visibility of the lean-to blind and the sound of rushing water masked their arrival. She burst out of hiding and ran in the opposite direction, later vetoing that nest from the project too. Three other jungle nests offered ample understorey vegetation where she could hide from the birds. Even giant squirrels and langurs didn’t blow her cover.
The plantation birds, however, didn’t worry about people standing in the open or automobiles driving past their nest trees. In fact, the four-month nesting period coincides with the coffee-picking season. If these males were as shy as that forest resident, the females would have starved.
Pawar spent more than 500 hours watching and recording the males’ visits to the nest, listing and counting the fruits and other food items they brought. By comparing the quality and quantity of the incarcerated females’ diets, the researcher could see the effect of the birds’ habitats. Forest hornbills ate more variety of fruits. Since estates have fewer fruiting trees, the hornbills compensated for the lack of diversity by eating a range of animals such as lizards, squirrels, snakes and even other bird chicks.
When the hornbill chicks are half-grown, the mothers break out of their self-imposed two-month confinement and assume a typical maternal task: feeding the young.
Janaki Lenin is not a conservationista but many creatures share her home for reasons she is yet to discover.
