Long-billed Partridge (Rhizothera longirostris) is being split: list R. dulitensis as Vulnerable and R. longirostris as Near Threatened?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for non-passerines

Lynx Edicions and BirdLife International will soon publish the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 1 of the checklist (for non-passerines) will begin to be incorporated into the 2013 Red List update, with the remainder, and those for passerines (which will appear in volume 2 of the checklist), to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

Long-billed Partridge Rhizothera longirostris is being split into R. longirostris and R. dulitensis following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, R. longirostris (BirdLife species factsheet) was listed as Near Threatened under criteria A2c+3c+4c, on the basis that it was suspected to be undergoing a moderately rapid population decline (approaching 30% over three generations [c.12 years]) owing to on-going habitat loss and degradation.

R. dulitensis is known to inhabit forest in a few montane areas in northern Borneo, and appears to have a disjunct range (Madge and McGowan 2002, Mann 2008, Myers 2009, Phillipps and Phillipps 2011). It may qualify as Vulnerable under criterion C2a(i), on the basis that the species could have a very small population (perhaps fewer than 2,500 mature individuals, given the paucity of records) which is inferred to be in decline owing to habitat loss and degradation in some areas, with all subpopulations perhaps numbering fewer than 1,000 mature individuals.

R. longirostris (as defined following the taxonomic change) inhabits primary forest, mature secondary growth, dry forest and areas of bamboo, mainly in the lowlands and hills of the Thai-Malay Peninsula, Sumatra and Borneo (del Hoyo et al. 1994, Madge and McGowan 2002). It may warrant listing as Near Threatened under criteria A2c+3c+4c, as it could be undergoing a moderately rapid population decline (approaching 30% over three generations [c.12 years]) owing to on-going habitat loss and degradation.

Comments on these suggested categories are invited and further information would be welcomed.

References:

del Hoyo, J., Elliott, A. and Sargatal, J. (1994) Handbook of the birds of the world, Vol 2: New World Vultures to Guineafowl. Barcelona, Spain: Lynx Edicions.

Madge, S. and McGowan, P. (2002) Pheasants, partridges and grouse: including buttonquails, sandgrouse and allies. London: Christopher Helm (Helm Identification Guide).

Mann, C. F. (2008) The Birds of Borneo: An Annotated Checklist. BOU Checklist No 23. Peterborough, UK: British Ornithologists’ Union and British Ornithologists’ Club.

Myers, S. (2009) A field guide to the birds of Borneo. London, UK: New Holland.

Phillipps, Q. and Phillipps, K. (2011) Phillipps’ field guide to the birds of Borneo. Second edition. London, UK: John Beaufoy Publishing.

Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. (2010) Quantitative criteria for species delimitation. Ibis 152: 724–746.

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