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.
Olive-flanked Robin-chat Cossypha anomala is being moved to genus Dessonornis and split into D. anomala, D. macclounii and D. mbuluensis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Olive-flanked Robin-chat was listed as Least Concern, on the basis that it did not approach the threshold for Vulnerable. Most of the pre-split species’s range is now encompassed within the newly defined Dessonornis macclounii. This species is found in eastern, southern and south-western Tanzania as well as northern Malawi and adjacent north-eastern Zambia. It utilises evergreen forest, as well as forest edge and patches, and gardens with dense understorey (Collar 2016). In Malawi, on the Nyika Plateau, its abundance is related to the density of understorey, and it may be scarce throughout the rest of its range (Collar 2016). However, this species is not thought to approach the threshold for Vulnerable under any criteria and so it is proposed that D. macclounii be listed as Least Concern.
D. anomala (as now defined following the taxonomic change) has a fragmented range, being found only in dense understorey of forested habitats on Mount Mulanji, Malawi and Mount Namuli in Mozambique (Collar 2016). It is abundant on Mount Mulanji (Collar 2016), but the global population has not been quantified. In November 2007, it was noted that the extent of mid-altitude forest on the eastern slopes of Mt Namuli was in decline (F. Dowsett-Lemairein litt. 2008), with threats including fires, encroachment by settlements and iron-smelting. In the past, forest has also been lost on Mount Mulanji (Dowsett-Lemaire 1989), and such habitat loss may be continuing. Therefore, given its restricted, and fragmented range it is proposed that this species warrants listing at least as Vulnerable under criterion B1ab(ii,iii,v).
D. mbuluensis is found in dense understorey of montane forest habitats in the Mbulu Highlands of northern Tanzania (Collar 2016). While potentially scarce (Collar 2016), population density estimates for the pre-split species (see Collar 2016) would still lead to this species not approaching the threshold for Vulnerable. Anthropogenic habitat alteration has occurred in the region (see BirdLife International 2016), but it is uncertain to what extent the montane region inhabited by this species has been affected by these processes. We request any further information regarding possible habitat and population trends for this species, and whether this may be causing any fragmentation of the population. In the absence of any information it is likely that this species will warrant listing as Least Concern.
Comments are invited on these proposed categories and further information would be welcomed.
BirdLife International 2016. Important Bird and Biodiversity Area factsheet: Lake Manyara. Downloaded from http://www.birdlife.org on 29/09/2016
Collar, N. 2016. Olive-flanked Robin-chat (Cossypha anomala). 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/58441 on 29 September 2016).
Dowsett-Lemaire, F. 1989. Ecological and biogeographical aspects of forest bird communities in Malawi. Scopus 13: 1-80.
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.
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.