Archived 2014 discussion: Green Imperial-pigeon (Ducula aenea) is being split: list D. oenothorax as Near Threatened?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for non-passerines

Lynx Edicions and BirdLife International will soon publish 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 1 of the checklist (for non-passerines) will begin to be incorporated into the 2014 Red List update, with the remainder, and those for passerines (which will appear in volume 2 of the checklist), 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.

Green Imperial-pigeon Ducula aenea is being split into D. aenea and D. oenothorax, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, D. aenea (BirdLife species factsheet) was listed as being of Least Concern, on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.

D. oenothorax is endemic to the island of Enggano, west of southern Sumatra, Indonesia (Gibbs et al. 2001). The pre-split species was characterised as occurring in a variety of wooded habitats, including modified areas, from primary and secondary forest to savanna woodland, mangroves and agricultural areas with remnant trees (Gibbs et al. 2001). It is assumed here that D. oenothorax shows similar habitat preferences; however, more information would be welcomed. The level of habitat loss on Enggano thus far has been described as minimal; however, recent tentative proposals for agricultural development imply that agricultural expansion could accelerate in the future (BirdLife International 2013a,b). Currently, areas of degraded forest are said to be very widespread on Enggano (Verbelen 2009), thus if the species is able to utilise this habitat it is unlikely to have been very affected by habitat degradation.

It is suggested that this species be listed as Near Threatened under criterion C2a(ii), on the basis that it probably has a small population, likely to include fewer than 10,000 mature individuals, forming a single subpopulation, which may experience a continuing decline in the near future owing to the expected loss and degradation of habitat through agricultural conversion, although there is uncertainty over this.

Any evidence that the species is hunted or not able to tolerate habitat modification would imply that it is currently undergoing a population decline and would suggest that it qualifies as Vulnerable under criterion C2a(ii), and could qualify as threatened or Near Threatened under criterion B1, owing to its very small range (with an estimated Extent of Occurrence of c.400 km2), but dependent on whether its habitat is considered very or severely fragmented (approaching or over 50% in patches too small to support viable populations).

D. aenea (as defined following the taxonomic change, and incorporating all other forms) is very widespread, occurring mainly in South and South-East Asia, and is likely to be listed as being of Least Concern, on the basis that it is not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.

Comments on these suggested categories and further information would be welcomed.

References:

BirdLife International (2013a) Species factsheet: Otus enganensis. Downloaded from: www.birdlife.org on 21/03/2013.

BirdLife International (2013b) Species factsheet: Zoothera leucolaema. Downloaded from: www.birdlife.org on 21/03/2013.

Gibbs, D., Barnes, E. and Cox, J. (2001) Pigeons and doves: a guide to the pigeons and doves of the world. Robertsbridge, U.K.: Pica Press.

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.

Verbelen, P. (2009) The Enggano Thrush Zoothera leucolaema with some notes on its vocalisations. BirdingASIA 12: 62–64.

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2 Responses to Archived 2014 discussion: Green Imperial-pigeon (Ducula aenea) is being split: list D. oenothorax as Near Threatened?

  1. Joe Taylor says:

    Preliminary proposals

    Based on available information, our preliminary proposals for the 2014 Red List would be to treat:

    D. aenea as Least Concern

    D. oenothorax as Near Threatened under criterion C2a(ii)

    There is now a period for further comments until the final deadline of 31 March, after which recommended categorisations will be put forward to IUCN.

    The final Red List categories will be published on the BirdLife and IUCN websites in mid-2014, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  2. Andy Symes says:

    Recommended categorisations to be put forward to IUCN

    Following further review, there have been no changes to our preliminary proposals for the 2014 Red List status of these species.

    The final categorisations will be published later in 2014, following further checking of information relevant to the assessments by BirdLife and IUCN.

Comments are closed.