Of Bombu Fruits and Hornbill Love

Coming back after the Kudu tour, I found myself guiding two short tours from 21-23, January—with Brian and Isabel Eady, two keen birders from Suffolk, England. The first was a day excursion to the dry lowlands of Sigiriya to explore the climax forest that envelopes the Sigiriya Rock. The second tour was a 2-day affair, and it took us to the endemic hotspot, Sinharaja ‘World Heritage’ rain forest, in the moist southwestern interior.

During these two coordinated birding raids, we were able to rake in twenty-seven endemic birds, out of the thirty-three currently recognised; plus a tally of over hundred other species of birds. Our hits and misses, thrills and spills, and other juicy details are in a trip report done by Brian.

In the meantime, here are a few highlights from my perspective.

Top birding highlight: A brooding male Sri Lanka Frogmouth in a nest, with a chick bursting out of its rim. In this species, the male attends to looking after the young during the daytime—when the female chills in a cool hideaway not too far.

Top garden bird: An Indian Pitta that I found in my backyard when the Eadys dropped by at my place.

Top spotting: A vocal Chestnut-backed Owlet, about 35m high up in a canopy giant.

Top forest bird: Sri Lanka Scaly Thrush.
I lured it by mimicking its high-pitched contact call, which I have sort of mastered now. This rendition is inaudible for the senior citizens, as is the call of the bird.

Top behavioural observation: An attempted courtship feeding by a pair Sri Lanka Grey Hornbills. This was what happened. No, first, a quick preamble on Hornbill breeding strategy. In hornbills (African Ground Hornbills excepted), the female imprisons herself inside a tree cavity to lay eggs, and to raise chicks, during which period the male delivers food to her and chicks.

In species such as Sri Lanka Grey Hornbill, which engages in cooperate breeding, the male is aided by a team of mostly younger members, which eases his burden. They, in turn, reap in important life lessons—on what it takes to be a real hornbill parent later on in their lives.

Most hornbills use mud to cover the opening of the cavity first. Before the door of the cavity becomes too small—for the female to squeeze into—she enters it, and begins to cover it from inside using regurgitated food and her bodily excretions. Finally, the opening of the nest hole is reduced to a narrow slit, just wide enough for the male to poke its beak to deliver food inside. And for the female to eject her waste material—for better nest-sanitation.

Most females undergo moult during this imprisonment: when she sheds her flight feathers, and grows them newly. Those feathers she loses in turn provide a soft bedding for the young.

The nesthole is broken by the female when the young are ready to fledge. In some species, the female frees herself out, to join the male in feeding the young, as their nutritional needs increase. The chicks in such cases are smart enough to seal the cavity from inside, until they are ready to meet the challenges of the outside world.

Coming back to courtship feeding, it is an important pair-bonding strategy used by the male bird to show his 'quality'—as a genuine breadwinner. For all the sacrifices she has to make in the evolutionary business of give and take, the female does not want to get stuck inside a dingy tree hole with poor facilities, and find that her partner is unable to deliver. For all what we know, she may not even have flight feathers by the time she realises this.

On this occasion, as the male offered a tiny fruit of Bombu Symplocos cochinchinensis, held delicately between his powerful mandibles, the female gave the cold shoulder, and took wing. I sensed her saying, "If you want me, you gotta do more than that."

And probably murmuring to herself, "What a cheapskate!", as she left him looking desponded like this:

I concede that it wasn’t a huge reward.

The Bombu trees at Sinharaja rain forest were bursting with fruit, and were magnets for all types of birds. These included the Sri Lanka Wood Pigeon, a highland endemic that descends to lowland forests such as Sinharaja during peak fruiting times. I also accept that it was not difficult for a female hornbill to reach one of those Bombu trees in fruit to help herself.

But the point is—that tiny Bombu fruit was offered to her with love.

Why o’why didn't she accept it?