Serendipitous species discovery in Sri Lanka
"It is most improbable that a bird entirely new to science could now exist in Ceylon," a foremost authority on Sri Lankan birdlife wrote in 1951. Just over half a century later, a new Scops-owl – a bird totally overlooked by collectors and field naturalists – has been added to the list of Sri Lanka's endemics.
In February 1995, Deepal H. Warakagoda first heard and tape-recorded an unfamiliar owl-like call at night in Kitulgala Proposed Reserve, a rainforest in the wet zone of Sri Lanka. Over the next six years he heard the call several more times, at Kitulgala and at Sinharaja Forest Reserve, but was never able to observe the calling bird.
Deepal compared the recording to other Asian owls, and sent it to Pamela Rasmussen, who agreed that while it sounded like an owl, it did not match any of the species known to occur in Sri Lanka, although it was most like Reddish Scops-owl Otus rufescens.
"The possibility of a new species of owl in a country as well-known ornithologically as Sri Lanka, where the last new bird species was described as long ago as 1868, seemed very remote. However, Scops-owls are notoriously easily overlooked and some species are cryptically similar." —Deepal H. Warakagoda
Deepal eventually succeeded in observing the bird, for several minutes, at Sinharaja FR in January 2001. It was a very small rufous earless owl, quite unlike any other on the island or anywhere else in South Asia. In February 2001, wildlife photographer Chandima Kahandawala obtained pictures of the bird from many different angles.
From these photographs, Deepal was able to confirm that the owl is strikingly distinct in many characteristics from other Sri Lankan species. "Among scops-owls it appears most similar to O. rufescens, and yet shows numerous differences."
In August 2001 a male was mist-netted, studied, photographed, ringed and released, and biometrics, descriptions and photographs sent to Pamela Rasmussen. Searches of museums with significant Sri Lankan holdings found no overlooked specimens that could be used as a basis for description. "Given the distinctiveness of the owl, we believe it is unlikely that any such misidentified specimens exist," Deepal explained. "Therefore it was essential to collect a specimen of the new owl, but we were reluctant to do so at this stage because its population and conservation status were unknown "
By May 2002, a study launched by Deepal and colleagues, under the auspices of the Department of Wildlife Conservation and Forest Department of Sri Lanka, had found the new owl in five different forests, and detected at least 24 individuals. Permission to collect a specimen to be designated the type was granted, and the specimen obtained in November 2002.
Serendib Scops-0wl Otus thilohoffmanni is a small, short-tailed, rather uniformly rufescent scops-owl with eye colour ranging from yellow to orange, according to sex, lacking apparent ear-tufts, with a weakly-defined facial disk, and with weak tarsi feathered for less than half their length. Among Sri Lankan species, O.thilohoffmanni could be confused only with the Sri-Lankan race of Oriental Scops-owl, O. sunia leggei. It replaces Indian Scops-owl O. bakkamoena in the rainforests of the wet zone.
"We propose that Serendib Scops-owl is categorised as Endangered." —Deepal H. Warakagoda
O.thilohoffmanni roosts near the ground, where its colouration, size and shape camouflage it very well among dry and dead leaves. Essentially a nocturnal forest bird of secretive habits, it, begins calling at dusk, but remains at its roost until darkness falls, when it starts to hunt, still calling. It has been seen catching beetles and moths. When hunting in undergrowth it perches on thin angled and vertical twigs and stems; its small, weak legs and toes may be an adaptation enabling it to do this. When resting it often assumes a "relaxed" position, rather hunched, with its eyes partially closed and its feathers somewhat fluffed. Its vocal activity peaks again in the two hours before dawn.
O. thilohoffmanni has been found only in the lowland rainforests of the south-west quarter of the island: Kitulgala, Kanneliya and Eratna Gilimale, with its strongholds in the Sinharaja and Morapitiya-Runakana reserves, which are contiguous. These forests are all protected areas managed by the Forest Department of Sri Lanka. The species apparently requires a large, fairly intact are of rainforest; it has not been found in patches smaller than 8.2km.
A total of 45 individuals were known from these sites as of January 2004. Deepal believes that more are living in these five forests. "However, from the data gathered, the species occupies quite a restricted range within Sri Lanka. The total extent of the five forests is 230 km², and this can be considered the extent of occurrence of the species as known so far. As a result, we propose that Serendib Scops-owl is categorised as Endangered."
The description of Serendib Scops-owl was first published in Bull. B.O.C. vol 124, no. 2 June 2004
Credits: Nick Langley