New warbler bird species discovered in Vietnam

Matt Walker, BBC News 15 Dec 09;

A new species of warbler has been discovered in the forests of Vietnam and Laos.

The small green and yellow bird was first sighted in 1994, but at the time was thought to be a different species surviving 1000km from its usual home.
Now studies of the bird's morphology, DNA and vocalisations have confirmed it to be a unique species. Scientists have named it the Limestone leaf warbler.

Details of the bird's discovery are published in the journal Ibis.

"The bird was first seen at one place in Vietnam in July 1994 and again at the same place in April the following year, and in one area in central Laos in May 1995," says taxonomist Professor Per Alstrom of the Swedish Species Information Centre, a part of the Swedish University of Agricultural Sciences in Uppsala.

"Initially, the bird was identified as a Sulphur-breasted warbler, in itself an interesting finding, since it was apparently breeding more than 1000km south of its previously known breeding areas in China.

"Later it was realised that its songs differed markedly from the songs of the Sulphur-breasted warbler, and further studies were undertaken."

These studies by Prof Alstrom and colleagues, who included scientists from the Wildlife Conservation Society's Lao Program and Birdlife International in Indochina, confirmed the bird's unique identity.

Distinct voice

The plumage of the Limestone leaf warbler (Phylloscopus calciatilis) is almost identical to that of the Sulphur-breasted warbler (Phylloscopus ricketti), though the new species appears to have a colder yellow chest and more grey topside and stripped crown.

But the new species is smaller, with shorter wings, rounder wing tips and a proportionately larger bill.

"Its vocalisations, both song and contact call, are markedly different from those of the Sulphur-breasted warbler," says Professor Alstrom.

DNA analyses also suggest that it is more closely related to the Yellow-vented warbler (Phylloscopus cantator) from eastern Himalayas, northern Laos and adjacent part of China, which is quite different in plumage.

So the new species looks markedly different to its closest relative, Professor Alstrom explains, but very similar to its more distant relative.

"The most likely explanation [for this]," he says, "is that the plumages have not diverged much in the Sulphur-breasted and Limestone warblers since they separated from a common ancestor."

Surprisingly, the Yellow-vented warbler and the Limestone leaf warbler separated from a common ancestor much later, but have diverged much more in plumage.

The vocalisations have similarly diverged in all three species.

"Leaf warblers and many other warblers are renowned for being very similar-looking, while having distinct vocalisations, so it is very likely that other new species of warblers will be discovered," says Professor Alstrom.

Despite being unknown to science as a new species until now, the Limestone leaf warbler is quite numerous.

Professor Alstrom's team believes that the bird inhabits limestone karst habitats in Vietnam and Laos, and may also breed in several locations in southern China.

One other new species, the Bare-faced bulbul (Pycnonotus hualon), was described earlier this year from central Laos. Its habitat is similar to the Limestone leaf warbler, which highlights the ecological importance of the region.

New Warbler Discovered in Laos
ScienceDaily 21 Dec 09;

A diminutive, colorful bird living in the rocky forests of Laos and Vietnam has been discovered by a team of scientists from the Wildlife Conservation Society, Lao PDR Department of Forestry, Swedish University of Agricultural Science, Swedish Museum of Natural History, BirdLife International and other groups.

Named the "limestone leaf warbler" because it breeds in Laos's limestone karst environments -- a region known for unusual wildlife -- it is similar to other warblers in this area of Southeast Asia, except for its distinct vocalizations and slight morphological differences.

A description of the new species is published in the journal IBIS (The International Journal of Avian Science). Authors include: Per Alstrom, Swedish University of Agricultural Science and the Swedish Museum of Natural History; Peter Davidson, J. William Duckworth and Robert Timmins, Wildlife Conservation Society; Jonathan C. Eames and Trai Trong Le, Birdlife International in Indochina; Cu Nguyen, Vietnam Academy of Science and Technology; Urban Olsson, University of Goteborg; and biologist Craig Robson.

"The discovery of this new species is very exciting and underscores the importance of this region of Indochina for conservation," said Colin Poole, Executive Director of the Asia Program for the Wildlife Conservation Society. "With increased attention from biologists, the Annamite mountain range of Laos in particular is revealing itself as a Lost World for new and unusual wildlife."

The tiny bird is greenish-olive with a yellow breast and striped crown. Although it looks similar to other warblers, it is smaller with shorter wings and a larger bill than its closest relative the sulfur-breasted leaf warbler.

According to the study, the bird has a loud and distinct call, which is what first alerted the authors that the bird may be new to science.

Scientists presume there are many limestone leaf warblers in this region. But its habitat isn't without threats. Many parts of the species' native forests have been cleared as a result of wood collection. WCS is continuing to work with the Lao Government in an effort to reduce the threats limestone leaf warblers and other wildlife face in this region.

Earlier this year from this same region, a team of scientists from WCS and the University of Melbourne described the bare-faced bulbul -- another species previously unknown to science. In 2002 in this same area, Robert Timmins of WCS described the Kha-nyou, a newly discovered species of rodent so unusual it represented the lone surviving member of an otherwise entirely extinct family. Three years earlier, he described a unique striped rabbit in the region also new to science.