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.
Brown-headed Nuthatch Sitta pusilla is being split into S. pusilla and S. insularis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, S. pusilla (http://www.birdlife.org/datazone/species/factsheet/22711173) was listed as Least Concern on the basis that it did not approach the threshold for any criteria to be listed as Vulnerable. S. pusilla (as defined now following the taxonomic change) is found in the southeast of mainland USA in pine woodland (Harrap 2016). Analyses of trend data from the North American Breeding Bird Survey suggest a 24% decline between 1966 and 2013 (Sauer et al. 2014). However, analyses of the trend between 2003 and 2013 shows only a non-significant decline of 0.2% per year during that time period (Sauer et al. 2014). It is described as common in most of its range (Harrap 2016), and so is thought not to approach the threshold for Vulnerable under any criteria. Thus it is suggested that it should be listed as Least Concern.
S. insularis is found only on Grand Bahama Island of the Bahamas (Harrap 2016). Surveys in the early 1990s suggested that this species may have declined by as much as 90% since 1969 (Smith and Smith 1994), but more recent trends are not known. A population estimate of 1,800 individuals (equivalent to 1,200 mature individuals) was made in 2004, but the authors stated that this may be an optimistic number (Hayes et al. 2004). It is threatened by habitat destruction and degradation through logging and development; as well as fires and hurricane damage (Hayes et al. 2004). Invasive species may also be an issue, either acting as predators (Corn Snake, Elaphe guttata) or as competition for this species (e.g. House Sparrow, Passer domesticus, and European Starling, Sturnus vulgaris) (Hayes et al. 2004). Therefore it is proposed that this species be listed as Endangered, at least under criterion C2a(ii). Further information about more recent trends (over the past 12 years, which equates to 3 generations for this species) would be welcomed.
Comments are invited on these proposed categories.
Harrap, S. (2016). Brown-headed Nuthatch (Sitta pusilla). 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/59923 on 30 August 2016).
Hayes, W. K., Barry, R. X., McKenzie, Z. and Barry, P. (2004) Grand Bahama’s brown-headed nuthatch: a distinct and endangered species. Bahamas Journal of Science 12(1): 21-28.
Sauer, J. R., Hines, J. E., Fallon, J. E., Pardieck, K. L., Ziolkowski, Jr., D. J., and Link, W. A. (2014) The North American Breeding Bird Survey, Results and Analysis 1966 – 2013. Version 01.30.2015 USGS Patuxent Wildlife Research Center, Laurel, MD.
Smith, P. W. and Smith, S. A. (1994) Preliminary assessment of the brown-headed nuthatch in the Bahamas. Bahamas Journal of Science 1: 22-26.
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.