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.
Kerala Laughingthrush Strophocincla fairbanki is being moved to genus Trochalopteron and split into T. fairbanki and T. meridionale, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Kerala Laughingthrush was listed as Near Threatened under criterion B1ab(i,ii,iii,iv,v), on the basis that it had a ‘small global range, and is likely to be declining as a result of habitat loss. However, it is able to persist in some degraded habitats, suggesting that it may not be at imminent risk’ (BirdLife International 2016). Trochalopteron fairbanki (as now defined following the taxonomic change) is found in the Western Ghats south of the Palakkad gap until the Shenogottah (=Achenkovil) gap (see Praveen J. and Nameer 2012). T. meridionale is found further south of this in the Agasthyamalai hills (Praveen J. and Nameer 2012). The pre-split species was found in a range of habitats and can tolerate habitat degradation, occurring in plantations, scrub, secondary forest, gardens, and forest edge (Collar and Robson 2016).
Both species are range restricted with possible Extents of Occurrence <5,000km2 (Praveen J. and Nameer 2016), pending Minimum Convex Polygon analyses. There is forest destruction occurring within both species’s ranges (see Hansen et al. 2013), which may be reducing the area/quality of available habitat; though their tolerance for habitat degradation may mean that any population declines will be slow. They may not qualify as threatened under criterion B1, though, as it is not certain to what extent each species may be severely fragmented rather than just fragmented (see IUCN 2001, 2012) and rates of forest loss suggest both species may be found at >10 locations*.
The population size of both species has not been quantified, but the species has been described as locally ‘fairly common’ (del Hoyo et al. 2007). Based on known records and range size the population size of T. fairbanki likely exceeds 10,000 mature individuals and would not approach the threshold for Vulnerable under criterion C. The population size of T. meridionale may be estimated at 2,500-9,999 mature individuals, which fits with population density estimates for congeners and an assumption that only a proportion of its range is occupied. Therefore, T. meridionale may qualify as Vulnerable under criterion C2a(ii). In the absence of any further information regarding the degree of fragmentation of the population of T. fairbanki, it is suggested that this species be listed as Near Threatened under criterion B1ab(iii,v).
Comments are invited on these proposed categories and further information would be welcomed.
*Note that the term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat (IUCN 2001, 2012).
Collar, N. and Robson, C. 2016. Kerala Laughingthrush (Strophocincla fairbanki). 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/59617 on 12 October 2016).
del Hoyo, J., Elliott, A. and Christie, D. 2007. Handbook of the Birds of the World, vol. 12: Picathartes to Tits and Chickadees. Lynx Edicions, Barcelona, Spain.
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
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.
IUCN. 2012. Guidelines for Application of IUCN Red List Criteria at Regional and National Levels: Version 4.0. Gland, Switzerland and Cambridge, UK: IUCN.
Praveen J. and Nameer, P.O. 2012. Strophocincla Laughingthrushes of South India: a case for allopatric speciation and impact on their conservation. J. Bombay Nat. Hist. Soc. 109: 46-52.
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.