Sinharaja bird wave – On the wings of a wildlife spectacle

The Sinharaja rainforest’s ‘Mixed Species Feeding Bird Flocks’ is a unique spectacle that can also be promoted as a tourist attraction, a leading zoologist said recently. Addressing a gathering of wildlife enthusiasts and tourism industry representatives at a lecture titled “Sinharaja Bird Wave” at the Ceylon Chamber of Commerce auditorium, Prof. Sarath Kotagama, said that two or more species feeding and moving in the same direction is known as a ‘Mixed Species feeding flock’.

A painting that captures the mixed species flocks in Sinharaja

In Sinharaja, some of the flocks could have as many as 35-50 individual birds from dozens of different species. It is a spectacular sight and the usually silent Sinharaja forest erupts into a cacophony of bird calls for a few minutes, as the flock approaches. On an average, there could be about 12 different species of birds, with some flocks recording as much as 30 - 40 different birds. Some researchers have recorded flocks consisting of over hundred individuals.

The birds do not stay for a long time in one place, as they move forward all the while feeding. In a few minutes, the noise recedes and the forest is once again engulfed in silence. Bird flocks is a phenomenon well documented but least understood, Prof. Kotagama said. Researches have revealed its formation, function and other interesting scenarios.

The nucleus or the centric bird species that take the lead in forming the bird flocks are the Orange-billed Babbler and Crested Drongo. Usually, in the morning, the Crested Drongo that inhabits the forest canopy, starts calling, which is believed to be the wakeup call to other members of the flock. Then the Orange-billed Babblers start steering the flock forward.

The Sinharaja rainforest, as its name implies, receives plenty of rain. This feature hinders birds from locating food and therefore moving in a group helps them to find food. It is believed that this ‘feeding efficiency’ is one of the reasons for these flock formations. Interestingly, various birds travel in the flock at different levels. A rainforest can be divided into different levels, based on height and vegetation, namely ground, under storey, sub canopy, canopy, above canopy and emergent. Different birds specialise at different levels. For example, when the Orange-billed Babblers feed on the under storey, they disturb lots of insects which take flight. These become easy prey for the birds hovering above at canopy level.
Security is the other major advantage these birds enjoy moving as a unit. Many birds mean many eyes. So they are able to detect a predator and warn others, says Prof. Kotagama. An added advantage is that these birds move at different levels, so that dangers at all levels are covered. When a predator like an owl is present, some of the birds flock closely to mob the intruder. Unable to bear the continuous mobbing by the chattering birds the predator usually gives up and departs.

Prof. Sarath Kotagama

Prof. Kotagama said that researchers have also identified vocal signals used by the birds to communicate. Of them, the most important is the ‘alarm call’. The Crested Drongos play the role of sentinels, usually warning of any danger from above. As soon as the Drongos make the alarm call, the whole flock goes silent and ‘freezes’, so as not to reveal their location to the probable predator. Only after the Drongos give the ‘all clear’ call do they come out.

Bird watching is becoming popular around the world and Sri Lanka can easily be promoted as one such destination. However, it was important to highlight and present the unique features within the country, if we are to become an Ultimate Wildlife Safari as Sri Lanka Tourism is trying to promote. Citing ‘The Gathering’ which has been nominated as one of the 10 Best Wildlife Spectacular events of the world by LonelyPlanet, Prof. Kotagama said the mixed-species Bird Flocks can be presented to the Tourism industry as the ‘Sinharaja Bird Wave’.