Archived 2016 topics: Grey-cheeked Tit-babbler (Macronous flavicollis) is being moved to genus Mixornis and split: list M. flavicollis as Least Concern and M. prillwitzi as Vulnerable?

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.

Grey-cheeked Tit-babbler Macronous flavicollis is being moved to genus Mixornis and split into Mixornis flavicollis and M. prillwitzi, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, Grey-cheeked Tit-babbler was listed as Least Concern, on the basis that it did not approach the threshold for Vulnerable under any criterion. Mixornis flavicollis (as now defined following the taxonomic change) is known from Java and M. prillwitzi occurs on the Kangean Islands, Indonesia, and both are found in lowland forest and secondary growth habitats (Collar and Robson 2016). Extensive deforestation within both species’s range has greatly reduced the amount of available habitat, and deforestation continues on Java and in the Kangean Islands. M. flavicollis is fairly common at Ujung Kulon National Park, and common at Alas Purwo National Park (Collar and Robson 2016), but the widespread destruction of lowland forest on Java means that the remaining populations are now severely fragmented.

Based on known records, potential range size, and descriptions of abundance M. flavicollis likely has a population size that exceeds 10,000 mature individuals, but M. prillwitzi is estimated to have a population size of 2,500-9,999 mature individuals. These estimates are consistent with population density estimates of congeners and closely related species of a similar size, assuming only a proportion of their ranges are occupied. Each sub-population of M. prillwitzi also is estimated to be less than 1,000 mature individuals and so this species likely warrants listing as at least Vulnerable under criterion C2a(i). M. flavicollis, on the other hand, is thought to have a population size and range that are sufficiently large to not approach the threshold for Vulnerable, and rates of decline are not thought to approach the threshold for Vulnerable either (>30%  in the past c. 12 years) and so this species may warrant listing as Least Concern.

Comments are invited on these proposed categories and further information would be welcomed.

References:

Collar, N. and Robson, C. 2016. Grey-cheeked Tit-babbler (Macronus flavicollis). 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/59484 on 18 October 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.

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3 Responses to Archived 2016 topics: Grey-cheeked Tit-babbler (Macronous flavicollis) is being moved to genus Mixornis and split: list M. flavicollis as Least Concern and M. prillwitzi as Vulnerable?

  1. James Westrip (BirdLife) says:

    Based on available information, our preliminary proposal for the 2016 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.

    There is now a period for further comments until the final deadline of 28 October, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from those in the initial proposal.

    The final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  2. Bas van Balen says:

    Please note that lumping Mixornis prillwitzi with flavicollis was an error, as it is more related to gularis. This also means that it is less dependent on forest than flavicollis. Nevertheless, its restriction to only two islands (of which one is much smaller than the other) of this archipelago makes it vulnerable, but future is uncertain as there are a number of tiny, but densely populated islands inside the archipelago. There could be more development than there is now, of which the forestry practice of converting the forest into teak plantations is perhaps not even very harmful. Calling it vulnerable seems to be appropriate for the time being

  3. Rob Martin (BirdLife International) says:

    Comments have been received from Burung Indonesia (in litt. 2016) supporting the listing of Mixornis prillwitzi as Vulnerable.

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