This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for passerines
Lynx Edicions and BirdLife International will soon publish the second volume of 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 2 of the checklist (for passerines) will begin to be incorporated into the 2016 Red List update, with the remainder 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.
Short-tailed Scimitar-babbler Jabouilleia danjoui is being moved to genus Rimator and split into Rimator danjoui and R. naungmungensis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Short-tailed Scimitar-babbler was listed as Near Threatened under criteria A2c+3c+4c; C1+2a(i), on the basis that it was estimated to have a moderately small population which was suspected to be undergoing a moderately rapid decline due to deforestation within its range (BirdLife International 2016). R. danjoui (as now defined following the taxonomic change) is found in scattered localities throughout Vietnam and the species may also be potentially found in Laos (although no known reports in decade preceding 2011 [W. Duckwoth in litt. 2011]). It is very localised in its distribution, occurring in primary and secondary evergreen forest from 50-2,100 m (Collar and Robson 2016), though it can be absent from suitable areas of habitat (R. Craik in litt. 2011, S. Mahood in litt. 2011). Where it is found it can be ‘locally fairly common’, but it is ‘generally uncommon’ (Collar and Robson 2016), and the global population size is estimated to number 10,000-19,999 mature individuals. The rate of habitat loss over the past 3 generations of this species is likely to fall in the range of 1-19%, and so a similar rate of decline in the population size may be suspected. Therefore, the species likely does not approach the threshold for Vulnerable under criterion A. However, the localised nature of this species’s population, and the estimated moderately small population size means that the species may approach the threshold for Vulnerable under criterion C2a(i), and hence it is proposed that it be listed as Near Threatened under this criterion.
R. naungmungensis is known from the Naung Mung area of Kachin State in northern Myanmar, but its status is unclear (Collar and Robson 2016). The original specimens for this species were collected in primary forest with little human disturbance, and the species appears to favour the understorey of pre-montane rainforest (Rappole et al. 2005). The species has only been found in the Naung Mung area despite surveys in appropriate habitat in neighbouring areas (Rappole et al. 2005), and so the population is unlikely to be large, even though it might be fairly common in the Naung Mung area (Rappole et al. 2005). The species may fall into the range of 2,500-9,999 mature individuals, which would fit with population density estimates for congeners, and an assumption that only a proportion of its range is occupied. However, the lack of information regarding this species may suggest that its population size may in fact be smaller than this (250-2,499 mature individuals). Forest is being lost in this region (see Hansen et al. 2013), and so the species may be inferred to be in slow decline. Therefore, this species warrants listing at least as Vulnerable under criterion C2a(ii), and we request any further information or comments as to whether it may meet the threshold for Endangered (declining population size of <2,500 mature individuals with 95-100% of individuals in 1 sub-population).
Comments are invited on these proposed categories and further information would be welcomed.
BirdLife International 2016. Species factsheet: Jabouilleia danjoui. Downloaded from http://www.birdlife.org on 18/10/2016.
Collar, N. & Robson, C. 2016. Indochinese Wren-babbler (Rimator danjoui). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/59537 on 18 October 2016).
Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. Chini, C. O. Justice, and J. R. G. Townshend. 2013. High-Resolution Global Maps of 21st-Century Forest Cover Change. Science 342: 850–53. Data available on-line from: http://earthenginepartners.appspot.com/science-2013-global-forest. Accessed through Global Forest Watch on 10th October 2016. www.globalforestwatch.org
Rappole, J.H., Renner, S.C., Shwe, N.M. and Sweet, P.R. 2005. A new species of scimitar-babbler (Timaliidae: Jabouilleia) from the sub-Himalayan region of Myanmar. Auk 122: 1064-1069.
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.