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Rediscovery of Sillem's Mountain Finch

Male Sillem's Mountain Finch

Sillem's Mountain Finch Leucosticte sillemi is a species known only from two specimens collected by Dutch explorer Jérôme Alexander Sillem during the Netherlands Karakoram Expedition in 1929 from Kushku Maidan, a barren plateau in the Xinjiang Autonomous Region in western China, at an altitude of 5125m. One bird is a worn adult male, and the other a juvenile male with wings not yet fully grown (implying that the species bred in the area).

Both specimens languished in a mixed drawer of Leucosticte and Montifringilla finches in the collection of the Zoological Museum of Amsterdam, labelled as Brandt's Mountain Finch L. brandti, until Dutch ornithologist C. S. Roselaar noticed in 1991 that they did not match the other specimens in the drawer. A comparison with 400 specimens of L. brandti established that the birds represented a new species; in particular, the grey-fringed flight feathers, tawny-cinnamon head and neck, and an absence of black on the lores and forehead all serve to separate it from Brandt's Mountain Finch. In addition, the juvenile is heavily streaked above, unlike any juvenile Brandt's. He named the new species L. sillemi in a paper in the Bulletin of the British Ornithologists' Club in 1992.

OrientalBirdImages.org has photographs of the type specimens, kindly contributed by Dr. Roselaar.

Rediscovery in Qinghai in 2012

In early June 2012, Yann Muzika photographed many finches during a difficult trek in Yeniugou Valley in western Qinghai, China (1500km east of Kushku Maidan), including one he could not identify. In August, he sent a batch of photographs to Krys Kazmierczak, the maintainer of OrientalBirdImages.org, who immediately identified the mystery bird as the long-lost Sillem's Mountain Finch. The identity of the birds has been confirmed by various experts, including Dr. Roselaar. Upon studying the remaining photographs, some images of what appear to be the female (hitherto unknown) were also found.

A presumed female Sillem's Mountain Finch. The female was hitherto unknown.
Presumed female Sillem's Mountain Finch

Dr. Roselaar's paper describing the species speculates that, unlike other Leucosticte finches (in which the sexes are identical), the heavy streaking on the juvenile suggests that the adult female Sillem's Mountain Finch may look different from the male (which calls its taxonomy into question). Yann's photographs confirm this guess.

Click the photographs above for larger versions, or visit Yann's blog for an account of the rediscovery and more photographs (including some comparisons with Kozlowia roborowskii and Leucosticte brandti).

Further research is needed, which may include trapping the bird for measurements and close-up examination, as well as possibly procuring a blood sample for DNA analysis. The decision to make this news public at this stage was taken in order to encourage visitors to the remoter areas of the Tibetan plateau to look out for the species, so that we may learn more about its distribution and habitat requirements and endeavour to ensure that it continues to survive.

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