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 are planning to publish a taxonomic 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 Lynx-BirdLife list will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). The new list 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 2013 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 welcome comments on these initial assessments. Please note that there will be opportunities to comment and provide input on the potential/proposed taxonomic decisions themselves elsewhere on the BirdLife forums.
Madagascar Turtle-dove Nesoenas picturata is being split into N. picturata and N. rostrata, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, N. picturata (BirdLife species factsheet) was listed as Least Concern on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN criteria. This species was estimated to have an extremely large range, and hence did not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence of less than 20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appeared to be stable, and hence the species did not approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). The population size has not been quantified, but it was not believed to approach the thresholds for Vulnerable under the population size criterion (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).
N. rostrata is endemic to the Seychelles (Gibbs et al. 2001), where it has become extremely scarce, probably lacking remnant viable populations (G. Rocamora in litt. 2012), and may no longer exist in its pure form. Gibbs et al. (2001) listed the form as still extant on Aride and Bird Island (which apparently retained the only known viable populations by the mid-1990s, although viable populations may have also persisted on Denis and Cousin Islands [G. Rocamora in litt. 2012]), and extirpated from Cousine, Cousin, Mahé and Praslin. However, it is thought that a few rostrata-type individuals still remain (Skerrett and Disley 2011), as there are recent records from Aride, Cousine, Cousin, Frégate and Mahé (Skerrett and Disley 2011, G. Rocamora in litt. 2012). It is suggested that the species be listed as Critically Endangered (Possibly Extinct) under criterion C2a(i), on the basis that there are thought to be fewer than 250 mature individuals remaining, with each subpopulation probably numbering no more than 50 mature individuals (although its dispersal capabilities may mean that its population effectively forms a single subpopulation), and on-going population declines are inferred owing to hybridisation with N. picturata. It is possible that there are no truly pure individuals of N. rostrata remaining, but further study is required.
N. picturata (as defined following the taxonomic change, and incorporating all other forms) is found throughout Madagascar, the Amirantes Islands, Aldabra, South Island in the Cosmoledo Atoll and the Comoros, and has been introduced to the Seychelles, Réunion, Mauritius and Diego Garcia in the Chagos Archipelago (Gibbs et al. 2001). It shows flexible habitat requirements (Gibbs et al. 2001) and is likely to qualify as Least Concern on the basis that it is not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.
Comments are invited on these suggested categories and further information would be welcomed.
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.
Skerrett, A. and Disley, T. (2011) Birds of Seychelles. Helm Field Guide. London, UK: Christopher Helm.
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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