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.
Scrub Greenlet (Hylophilus flavipes) is being split into H. flavipes, H. viridiflavus and H. insularis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, H. flavipes (BirdLife species factsheet) was listed as Least Concern on the basis that it did not approach any of the thresholds for listing as Vulnerable. The pre-split species was characterised as often common or abundant and frequently found in highly modified or regenerating habitats (Brewer 2016).
H. flavipes (as defined following the taxonomic change) is found throughout northern Colombia and north Venezuela, H. viridiflavus is found from south west Costa Rica through Panama (and Coiba Island). These two newly defined species are not considered to approach the thresholds for listing as Vulnerable under any of the criteria, and it is suggested that they should be listed as Least Concern.
Tobago Greenlet, H. insularis is found only on the island of Tobago, with a newly calculated extent of occurrence (EOO) of 350 km2. It is a common resident throughout the island, favouring scrub and forest edge (Kenefick et al. 2011). The population is estimated to number 2,500-9,999 individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals.
Given the species’ tolerance of disturbed habitats it is thought that the population is stable, but given the very small global range it could perhaps be at risk from stochastic events and invasive species that could plausibly threaten the population within a short time period. If this were the case it may warrant listing as Near Threatened, on the basis that the population may approach the threshold for listing as Vulnerable under criterion D2. If not, it should be listed as Least Concern, despite the restricted range.
Comments are invited on these proposed categories and further information would be welcomed.
Brewer, D. (2016). Scrub Greenlet (Hylophilus flavipes). 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/61282 on 30 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.
Kenefick, M., Restall, R. and Hayes, F. 2011. The birds of Trinidad and Tobago: second Edition. Bloomsbury Publishing. London.
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.