Archived 2016 topics: Rearrangement of Island Leaf-warbler Phylloscopus poliocephalus: list P. misoriensis as Least Concern and P. maforensis as Near Threatened or 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.

Island Leaf-warbler Phylloscopus poliocephalus is being rearranged; P. makirensis is being lumped with P. poliocephalus; while P. maforensis and P. misoriensis are being split off, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, P. poliocephalus and P. makirensis were listed as Least Concern, on the basis that they did not approach the threshold for Vulnerable under any criterion. P. poliocephalus (as now defined following the taxonomic change) is still not thought to approach the threshold for Vulnerable under any criterion, and hence it is proposed that it be listed as Least Concern.

P. misoriensis is only found on the island of Biak, in Geelvink Bay, Indonesia in primary and secondary forest (Pratt and Beehler 2015). Habitat loss within its restricted range may be causing a slow population decline, however the species likely occurs at >>10 locations* and so would not approach the threshold for listing as Vulnerable under criterion B. Based on population density estimates of congeners, and assuming only a proportion of habitat is occupied then the population size of this species likely exceeds 10,000 mature individuals. Therefore, this species likely does not approach the threshold for Vulnerable under any criterion and would warrant listing as Least Concern. We do however welcome any further comments regarding population size estimates to see whether the number of mature individuals in this species may in fact approach or meet the threshold for Vulnerable.

P. maforensis is found only in forest on the island of Numfor in Geelvink Bay, Indonesia (Pratt and Beehler 2015). Habitat loss within its restricted range may be causing a slow population decline, however the species likely occurs at >>10 locations* and so would not approach the threshold for listing as Vulnerable under criterion B. The population size has not been directly estimated but based on population density estimates of congeners, and assuming only a proportion of habitat is occupied, then the population size may fall in the region of 10,000 mature individuals. Thus the species may warrant listing as Near Threatened or Vulnerable under criterion C2a(ii). We request any further comments or information regarding population size and trend estimates, but in the absence of any further information it is conservatively suggested that this species be listed as Vulnerable under criterion C2a(ii).

*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).

References:

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.

Pratt, T.K. and Beehler, B. M. 2015. Birds of New Guinea. Princeton University Press, Princeton and Oxford.

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: Rearrangement of Island Leaf-warbler Phylloscopus poliocephalus: list P. misoriensis as Least Concern and P. maforensis as Near Threatened or Vulnerable?

  1. Guy Dutson says:

    P. misoriensis is relatively uncommon on Biak, at least an order of magnitude lower population density than most congeners. In 2012, I explored six forest sites over three days and recorded two individuals in old-growth forest at one site. I have led another three birding tours to Biak and not seen the species. Precautionary, the population could <10,000 mature individuals and hence qualify as VU or NT C2aii.

    P. maforensis is relatively uncommon on Numfor. One seen and another singing in patchy secondary forest in 2012. Its population density is less than that of most of congeners, and likely <10,000 mature individuals, supporting Vulnerable under criterion C2a(ii)

  2. James Westrip (BirdLife) says:

    Based on available information, our preliminary proposal for the 2016 Red List would be to list:

    P. poliocephalus as Least Concern.

    P. misoriensis and P. maforensis as Vulnerable under criterion C2a(ii).

    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 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.

  3. Rob Martin (BirdLife International) says:

    Comments have been received from Burung Indonesia (in litt. 2016) supporting the listing of both P. maforensis and P. misoriensis as Vulnerable.

Comments are closed.