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.
Tahiti Reed-warbler Acrocephalus caffer is being split into A. caffer, A. musae and A. longirostris, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, A. caffer was listed as Endangered under criteria B1ab(ii,iii,v);C2a(i), on the basis that it had a very small population and range. The population was restricted to (probably) only one island, where it was rare, localised and declining due to disturbance and habitat degradation (BirdLife International 2016).
The taxonomic change is unlikely to significantly change any of the details for this species, because A. musae (including A. m. garretti) was endemic to the islands of Raiatea and Huahine, and went extinct in the late 1800s or early 1900s (BirdLife International 2016). The other newly split species, A. longirostris, is known from Moorea, but has been considered extinct (BirdLife International 2016, Dyrcz and de Juana 2016). There have, however, been at least two unconfirmed reports of these species since 2000 (A. Gouni in litt.2007, Cibois et al. 2008, A. Gouni in litt. 2011).
The prior assessment of A. caffer did not treat these as definitive evidence that the species may remain extant on Moorea. Therefore, it is proposed that the newly-defined A. caffer, endemic to Tahiti, be listed as Endangered under criteria B1ab(ii,iii,v);C2a(i).
The unconfirmed reports of A. longirostris on Moorea suggest that this species may possibly be extant, but the lack of any definitive reports suggest that, if it is extant, the population size is likely very low (probably less than 50 mature individuals). Therefore, it is suggested that this species be listed as Critically Endangered (Possibly Extinct) under criterion D.
A. musae has not been recorded since theearly 1900s and should be listed as Extinct.
BirdLife International (2016) Species factsheet: Acrocephalus caffer. Downloaded from http://www.birdlife.org on 21/09/2016.
Cibois, A., Thibault, J.-C. and Pasquet, E. 2008. Systematics of the extinct reed warblers Acrocephalus of the Society Islands of eastern Polynesia. Ibis 150(2): 365-376.
Dyrcz, A. and de Juana, E. 2016. Tahiti Reed-warbler (Acrocephalus caffer). 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/58815 on 21 September 2016).
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.