26/03/2019
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New bulbul species described from Borneo

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A cryptic new species of bulbul, previously considered to be a variation of a polymorphic species, has been described from Borneo.

Cream-vented Bulbul Pycnonotus simplex was thought to vary in its appearance, more specifically showing either red or white (creamy-yellow) irises. However, mitochondrial DNA sequence comparisons have revealed a startling surprise: the two forms aren’t closely related at all and a new species has been hiding in plain sight.

The white-eyed birds are sister to Ashy-fronted Bulbul, which is endemic to Palawan Island in the south-west Philippines, while red-eyed birds are sister to the white-eyed Cream-vented Bulbuls found on the Thai-Malay Peninsula. DNA sequencing found that red-eyed Bornean birds differ by a mean of 14 per cent from white-eyed birds. By comparison, red-eyed Bornean birds differed by just 4 per cent from white-eyed birds of the Thai-Malay Peninsula.


Comparison of (A) 'Cream-eyed Bulbul' 'Pycnonotus pseudosimplex', which has been found to represent a new species, and (B) the red-eyed Bornean form of Cream-vented Bulbul Pycnonotus simplex.

The newly identified taxon, which has been dubbed Cream-eyed Bulbul Pycnonotus pseudosimplex, has been described from several type specimens across a large area of northern Borneo. As well as differing in iris colour from Cream-vented Bulbul, its plumage is also yellower on the throat and vent, creating greater contrast with the darker breast and flanks.

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The two taxa appear to be sympatric, sharing the same mature forest interior and edge habitat. Although previous authors have stated that white-eyed and red-eyed individuals co-occur throughout Borneo, the study suggests that the white-eyed P pseudosimplex is considerably rarer and perhaps more habitat restricted than its red-eyed counterpart.

 

Reference

Shakya, S B, Lim, H C, Moyle, R G, Rahman, M A, Lakim, M, and Sheldon, F H. 2019. A cryptic new species of bulbul from BorneoBulletin of the British Ornithologists' Club, 139(1):46-55 (2019). DOI: https://doi.org/10.25226/bboc.v139i1.2019.a3

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