Archived 2016 topics: Bridled White-eye (Zosterops conspicillatus) is being split: list Z. conspicillatus as Extinct and Z. saypani as Endangered?

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.

Bridled White-eye Zosterops conspicillatus is being split into Z. conspicillatus and Z. saypani, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, Z. conspicillatus was listed as Endangered under criteria A3e;B1ab(v), on the basis that it was projected to undergo a very rapid population decline owing to the establishment of brown tree-snake Boiga irregularis on Saipan (BirdLife International 2016). Z. conspicillatus (as now defined following the taxonomic split) was found only on Guam, and was reported to be common in 1828 (van Balen 2016). The population has since become more and more restricted in range, and the last known sighting was in 1983 (van Balen 2008). The reason for the decline is not entirely clear, but the introduction of the brown tree-snake B. irregularis is the most likely cause (van Balen 2016). There is little doubt that the species is no longer extant (G. Dutson in litt. 2011) and so it is proposed that this species be listed as Extinct.

Z. saypani is found on the islands of Saipan, Tinian and Aguijan in the Northern Mariana Islands (to U.S.A.). It inhabits a wide range of habitats from native forest through to urban areas (BirdLife International 2016). It is abundant within its range (see BirdLife International 2016), and the population size has been stable or increasing since 1982 (Camp et al. 2009, Amidon et al. 2014). However, the largest threat to this species is the brown tree-snake, B. irregularis, which has been introduced to Saipan and may be becoming established there (Rodda and Savidge 2007). This island constitutes >50% of the global population of the species, and given its drastic impact on Z. conspicillatus on Guam, its presence is projected to have a significant impact on the population of Z. saypani. Therefore, it is proposed that this species be listed as Endangered under criteria A3e+4e;B1ab(v).

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

References:

Amidon, F., Camp, R. J., Marshall, A. P., Pratt, T. K., Williams, L., Radley, P. and Cruz, J. B. 2014. Terrestrial bird population trends on Aguiguan (Goat Island), Mariana Islands. Bird Conservation International 24(4): 505-517.

BirdLife International 2016. Species factsheet: Zosterops conspicillatus. Downloaded from http://www.birdlife.org on 10/10/2016.

Camp, R. J., Pratt, T. K., Marshall, A. P., Amidon, F. and Williams, L. L. 2009. Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler (Acrocephalus luscinia). Bird Conservation International 19(4): 323-337.

Rodda, G.H., and Savidge, J .A. 2007. Biology and impacts of Pacific Island invasive species. 2. Boiga irregularis, the brown tree snake (Reptilia: Colubridae). Pacific Science 61: 307-324.

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.

van Balen, B. 2008. Family Zosteropidae (White-eyes). In Handbook of the Birds of the World Volume 13: Penduline-tits to Shrikes (J. del Hoyo, A. Elliott and D.A. Christie eds). Lynx Edicions, Barcelona.

van Balen, B. 2016. Bridled White-eye (Zosterops conspicillatus). 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/60166 on 10 October 2016).

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One Response to Archived 2016 topics: Bridled White-eye (Zosterops conspicillatus) is being split: list Z. conspicillatus as Extinct and Z. saypani as Endangered?

  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.

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