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.
Brown-chested Jungle-flycatcher Rhinomyias brunneatus is being moved to genus Cyornis and split into Cyornis brunneatus and C. nicobaricus, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Brown-chested Jungle-flycatcher was listed as Vulnerable under criterion C2a(ii), on the basis that it has a small and declining population as a result of destruction of its habitat on both in its breeding and wintering grounds (BirdLife International 2016a). This assessment did not include potential populations on the Andaman and Nicobar Islands because the status of these populations was not clear (BirdLife International 2016a). Therefore, an assessment Cyornis brunneatus (as now defined following the taxonomic change) would equate to the pre-split assessment. There is continuing loss of its bamboo undergrowth and forest habitat on both its wintering (peninsula Malaysia and Singapore [passage migrant in Thailand]) and breeding grounds (south-east China) (BirdLife International 2016a, Clement 2016). Its population size has been estimated at 2,500-9,999 mature individuals, which is consistent with population density estimates for congeners or closely related species and assuming only a proportion of its range is occupied (BirdLife Interantional 2016a). Therefore, this species qualifies as Vulnerable under criterion C2a(ii).
C. nicobaricus is a resident of Great and Little Nicobar Islands, occurring in forest and dense thickets/ bushes down to sea level (Clement 2016). The species has been described as common (Clement 2016), although it was not recorded during a survey of the Andaman and Nicobar Islands in 2007 (Pande et al. 2007). Using population density estimates of congeners (range c.10-90 individuals/km2), and assuming only a proportion of its range is occupied, the population size is likely in the range of 2,200-20,000 individuals, which roughly equates to 1,450-13,300 mature individuals. On the Nicobar Islands clearance and conversion of forests for plantations and infrastructure development are the most serious long-term threats, and so while the pre-split species was thought to be able to cope with a degree of habitat degradation (occurring in large gardens and secondary forest [Clement 2016]) the population is likely in decline. Despite a potentially small population size this species would not qualify as threatened under criterion C2a(i) or C2a(ii) because it is likely that one sub population does not contain >95% of the global population and the largest sub-population likely contains >1,000 mature individuals. However, its restricted range within which habitat loss is occurring means it would qualify as Near Threatened under criterion B1ab(ii,iii,v) in line with species with a similar distribution such as Nicobar Serpent-Eagle, Spilornis klossi (BirdLife International 2016b), as well as approaching the threshold for Vulnerable under criterion C2a(i). Therefore, it is proposed that this species be listed as Near Threatened under criteria B1ab(ii,iii,v);C2a(i).
Comments are invited on these proposed categories and further information would be welcomed.
BirdLife International 2016a. Species factsheet: Rhinomyias brunneatus. Downloaded from http://www.birdlife.org on 10/10/2016.
BirdLife International 2016b. Species factsheet: Spilornis klossi. Downloaded from http://www.birdlife.org on 10/10/2016.
Clement, P. 2016. Brown-chested Jungle-flycatcher (Rhinomyias brunneatus). 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/59012 on 10 October 2016).
Pande, S., Sant, N., Ranade, S., Pednekar, S., Mestry, P., Deshpande, P., Kharat, S. and Deshmukh, V. 2007. Avifaunal survey of Andaman and Nicobar Islands, January 2007. Indian Birds 3: 162-180.
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.