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.
Rufous-breasted Leaftosser Sclerurus scansor is being split into S. scansor and S. cearensis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, S. scansor was listed as Least Concern, on the basis that it did not approach the threshold for Vulnerable under any criterion. Both newly split species have large ranges. S. scansor (as now defined following the taxonomic change) is found in lowland and montane evergreen forest throughout central, central-eastern and south-eastern Brazil, as well as eastern Paraguay and north-eastern Argentina (Remsen 2016). S. cearensis is found in lowland to montane forest in north-eastern Brazil, from Ceará south to northern Bahia (Remsen 2016).
There has been extensive forest loss in both of the species’s ranges (see Global Forest Watch webpage: http://www.globalforestwatch.org/map), and these species may be very intolerant of any habitat alteration, with even selective logging affecting local abundance (Remsen 2016). Therefore, while forest clearance rates may not be at a rate sufficient to suggest population declines would approach the threshold for Vulnerable under criterion A2, declines may be occurring even in areas not completely cleared. Habitat clearance is likely to continue into the future, and it is suspected that the population of both of these species are declining at least at a slow or moderate rate.
However, S. scansor is not listed in the recent Brazilian national Red List and it is assumed to have been assessed and classified as Least Concern. The comparatively large number of observations of the species on WikiAves and eBird would seem to support this proposal.
S. cearensis is classified as Vulnerable on the Brazilian Red List under criterion B2, on the basis of its small Area of Occupancy (listed <2,000 km2 but no further details given), and a distribution which was apparently considered to be severely fragmented. The vast majority of recent records come from Ceará, with others from Pernambuco and Bahia (WikiAves).
Therefore, it is proposed that S. scansor be listed as Least Concern and S. cearensis be listed as Vulnerable, as assessed for the Brazilian Red List, unless additional information received suggests a different classification is warranted.
Comments are invited and further information would be welcomed.
Remsen, J.V., Jr 2016. Rufous-breasted Leaftosser (Sclerurus scansor). 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/56585 on 26 September 2016).
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.