FEEDING FLOCKS IN SINHARAJA
de Silva Wijeyeratne, G. (2003). Feeding Flocks in Sinharaja. LMD. July 2003. Page 142. Volume 09, Issue 12.
Gehan de Silva Wijeyeratne goes in search of a mixed species feeding flock
A stream, heavily laden with recent rains, roared down a rocky ravine. The air was damp. The leaf litter glistened and gleamed with wetness against the few rays of sunlight which penetrated into the forest floor. The undergrowth was sparse, as so little sunlight penetrated below the canopy to impart the life giving energy from the sun. One can see relatively far through this sparse undergrowth in this dimly lit underworld. The plants on the floor were victims of intense competition in the higher levels. The forest canopy was the edge of darkness and light. It was here that a fierce battle was being waged by the plants, to out compete each other in the race for the energy giving light. Down below, a few seeds which had taken root, waited patiently, in a suspended state of juvenile growth, until a forest giant fell, opening a window into the skies. To the untrained eye, many of the saplings on the floor look like seedlings which have recently sprouted. But research overseas have shown that some of these plants could be several decades old, waiting for a penetrating shaft of sunlight, created by a fallen forest giant to begin their race up to the sky.
Sanath Weerasingha and Dilshanee Samarasingha listened spell bound to my stories of the fierce competition waged in the seemingly placid world of plants. The two of them were journalists I had invited along to experience the magic of the rainforest. Having them to keep me company also had the bonus of having more hands to carry my equipment. I was beginning to think I could make it a habit to invite able bodied journalists along, on my excursions to the forest.
One of our targets on this visit was to seek out what is know as a mixed species feeding flock. Sinharaja has one of the best studied feeding flock systems in the world and can boast of probably the longest running study dating from the 1970s. A feeding flock works like a super organism. Different species of birds, sometimes over twenty different species, will work in unison in a flock. They sweep across the forest like a giant vacuum cleaner, devouring any prey in their path. Why birds assemble into flocks and in particular mixed species feeding flocks has for long fascinated scientists. It is clear that they must derive a benefit which surpasses that of feeding in single species flocks.
One obvious benefit is protection. With more birds there are more pairs of eyes to look out for danger. The feeding flocks in Sri Lankan lowland rainforests have taken this a stage further. They take with them, a security guard or a rather a pair of them. Rather interestingly, almost every significant feeding flock has a pair of Crested Drongos. They are seemingly ordinary, black coloured birds. Despite modest outward appearances, they make up in courage what they lack in visual appeal. These birds are rather plucky and will fearlessly attack even a sizeable bird of prey and ward it off. Consequently, it is not unusual to find other birds seeking a nest site near a Drongo’s nest. The Crested Drongo is also a nucleus species. Such a species being one which regularly occurs in a feeding flock and plays a central role in the social dynamics of it. Ornithologists have found that the Crested Drongo utter a special flock formation call to summon birds together. Another star in the nucleus species hierarchy is the Orange-billed Babbler. They keep up a constant medley of squeaks, scolding notes and chatter and seem to hold the flock together.
If one were to go in search of the elusive Red-faced Malkoha, one’s best chance would be to listen out for the Orange-billed Babbler. To the uninitiated this might seem puzzling. Not really, the Red-faced Malkoha is by and large silent, uttering at the most an occasional grunt. It is often a member of feeding flocks and discreetly occupies the mid and upper canopy. A person encountering a flock will be so mesmerized by the noise and movement of the Drongos and Babblers and brilliantly blue Black-naped Monarchs, the furtive Malkoha will be missed.
This is why expertise in eco-tourism is so important. I had invited Dilshanee and Sanath along for a practical example of how expertise makes the difference between seeing or not seeing a sought after species, the ‘value added premium’ in expert eco-tourism.
The first loud chatter we heard was a loud chorus of excited voices behind Amila Salgado who was leading an Expert Rainforest Tour to young children from an international school. He paused besides the gushing stream and pointed out the butterflies. A Blue Mormon and Common Birdwing competed in the size stakes. A Great Eggfly flashed past with silver and blue patches on its wings. A Commander winged by in its curious humped, stiff winged style of flight. In the undergrowth, a Glad-eye Bushbrown perched motionlessly, hoping to be overlooked as a dead leaf with a circle of fungus. Amila pointed to a large land snail, an Acavus species. He explained how village folk use its viscous secretion as a high energy drink. As expected this evoked sounds of astonishment and revulsion. Amila vanished into the forest like a Pied Piper. The forest fell silent again except for the constant roar of the gushing stream.
A loud belling note, harsh and metallic echoed through the forest. Peering into the gloom we watched a small family of Blue Magpies. With chocolate brown on their heads and wings and a red bill and feet, they look unreal. All too soon, the Blue Magpies flew away and we walked on, listening intently as we did.
An hour later, we heard the tell tale signs of a feeding flock, the calls of the Orange-billed Babblers. We waited patiently, perhaps over half an hour before they came into view. Soon, we saw the Crested Drongo and caught a glimpse of Red-faced Malkoha. Equally furtive was the gorgeous Malabar Trogon. The male with his brilliant crimson breast is distinctive, but is so cryptic in the multi-hued rainforest foliage. A pair of Legges Flowerpeckers dangled on some seed heads. From the canopy the sharp whistle of the scarce White-faced Starling betrayed its presence. More conspicuous were a number of endemic Yellow-fronted Barbets and Layards Parakeets.
A shrill, almost hysterical chatter came from the undergrowth. A flock of the rare Ashy-headed Laughing Thrushes were scouring the forest floor whilst their cousins the Orange-billed Babblers, higher up, distracted the on lookers. Eagerly, I positioned my self with my camera, poised to shoot. As the first Laughing Thrush came into view, the rain came down. Another five minutes more, would have made all the difference. I opened out my rain gear and covered my equipment. The journalists had left their umbrellas in the car, it had not looked like it would rain. The equipment was dry and the journalists very wet.
The writer is the CEO of a wildlife and adventure travel company. He is the lead author of A Birdwatcher’s Guide to Sri Lanka (OBC) and A Photographic Guide to the Birds of Sri Lanka (New Holland). To subscribe to his free, wildlife e-newsletter, e-mail him at firstname.lastname@example.org with “subscribe wildlife news” in the message header.