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.
Tropical Parula Parula pitiayumi is being moved to genus Setophaga and split into Setophaga pitiayumi and S. graysoni, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Tropical Parula was listed as Least Concern, on the basis that it did not approach the threshold for Vulnerable under any criterion. Setophaga pitiayumi (as now defined following the taxonomic change) retains much of the pre-split species’s range and population, being found from southern Texas, USA south to northern Argentina. It has declined in Texas (Curson 2016), but other data has suggested population increases in North America (Butcher and Niven 2007). The species is not thought to approach the threshold for Vulnerable under any criterion, and so it would warrant listing as Least Concern.
P. graysoni is known only from the Revillagigedo Islands, in particular Socorro, Mexico. The pre-split species inhabited a range of habitats, and surveys on Socorro found the species at relatively high densities in most habitats (Rodriguez-Estrella et al. 1996). The proliferation of sheep on the island since the 19th century has led to deforestation of large parts of the southern lowlands, but the sheep have recently been eradicated (Ortiz-Alcaraz et al. 2016), and the species was still present even in the most degraded habitat, although at lower densities than habitats of a lower level of degradation (Rodriguez-Estrella et al. 1996). Feral cats are however present on the island, which could pose a threat to this species, as could rats. Despite this the species is not expected to meet the threshold for Vulnerable under any criterion.
Socorro Wren, Troglodytes sissoni, is another common inhabitant of Socorro Island though more affected by habitat disturbance than S. graysoni (Rodriguez-Estrella et al. 1996). This species is listed as Near Threatened under criterion D2 because of its extremely small range (BirdLife International 2016). In the absence of any further information it is proposed that S. graysoni should be listed in line with T. sissoni as Near Threatened under criterion D2 given its highly restricted range.
Comments are invited on these proposed categories and further information would be welcomed.
BirdLife International 2016. Species factsheet: Troglodytes sissonii. Downloaded from http://www.birdlife.org on 05/10/2016.
Butcher, G. S. and Niven, D. K. 2007. Combining data from the Christmas bird count and the breeding bird survey to determine the continental status and trends of North American birds. National Audubon Society.
Curson, J. 2016. Tropical Parula (Parula pitiayumi). 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/61465 on 5 October 2016).
Ortiz-Alcaraz, A., Aguirre-Muñoz, A., Méndez-Sánchez and Ortega-Rubio, A. 2016. Feral sheep eradication at Socorro Island, Mexico: a mandatory step to ensure ecological restoration. Interciena 41: 184-189.
Rodriguez-Estrella, R., de la Luz, J. L. L., Breceda, A., Castellanos, A., Cancino, J. and Llinas, J. 1996. Status, density and habitat relationships of the endemic terrestrial birds of Socorro Island, Revillagigedo Islands, Mexico. Biol. Conserv. 76: 195-202.
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.