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.
Blue-breasted Flycatcher Cyornis herioti is being split into C. herioti and C. camarinensis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, C. herioti was listed as Least Concern, on the basis that it did not approach the threshold for Vulnerable under any criterion. C. herioti (as now defined following the taxonomic change) is found only in northern and central Luzon, while C. carmarinensis is confined to southern Luzon and Catanduanes (see Clement and de Juana 2016). The pre-split species was considered locally common in the northern part of its range (now corresponding to the newly defined C. herioti) (Poulsen 1995). They both inhabit lowland to submontane forest (Clement and de Juana 2016), but in the lowlands are rare (Poulsen 1995).
Extensive deforestation on Luzon has been the probable driver of such scarcity in the lowlands as the species’s habitat has been destroyed (Poulsen 1995), and this has likely led populations to decline and become severely fragmented. While habitat destruction is now at a lower rate than it was previously, the forests where this species live continue to be destroyed (see Hansen et al. 2013), and so populations likely continue to be in decline. Both species have been rarely recorded recently (see eBird webpage, http://ebird.org/), and C. camarinensis appears to have been scarcely recorded in the past (see Poulsen 1995). Deforestation has likely greatly reduced the amount of available habitat for these species, particularly C. camarinensis, and considering their apparent scarcity, the global population of both species is unlikely to be large. The population size and density has not been estimated for either species, but C. camarinensis is conservatively suspected to be less than 10,000 mature individuals, and possibly less than 2,500 mature individuals, based on known records, low population density estimates for closely related species and assuming only a proportion of its range is occupied. It is also assumed that the number of individuals in each subpopulation of C. camarinensis is likely less than 1,000 mature individuals, and therefore this species likely warrants listing as Vulnerable under criterion C2a(i).
Based on the same assumptions as for C. camarinensis the population size for C. herioti likely exceeds 10,000 mature individuals and each subpopulation in this species may contain more than 1,000 mature individuals. Thus the species likely does not qualify for a threatened category. However, considering the paucity of recent reports for this species it is conservatively suggested that this species be listed as Near Threatened under criterion C2a(i) as population and sub-population sizes may approach these thresholds, although we welcome any further information regarding these estimates in case they may be significantly over- or under-estimating the number of mature individuals that are present.
Comments are invited on these proposed categories and further information would be welcomed.
Clement, P. and de Juana, E. 2016. Blue-breasted Blue-flycatcher (Cyornis herioti). 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/59086 on 12 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
Poulsen, M.K. 1995. The threatened and near-threatened birds of Luzon, Philippines, and the role of the Sierra Madre mountains in their conservation. Bird Conservation International 5: 79-115.
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.