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.
Long-billed Tailorbird Artisornis moreaui is being split into A. moreaui and A. sousae, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Long-billed Tailorbird was listed as Critically Endangered under criterion C2a(ii), on the basis that it had a very small population, that was likely to be undergoing a decline due to habitat alteration and fragmentation, with >90% of the population in one subpopulation.
A. moreaui (as defined following the taxonomic change) is found in the forest edge and canopy gaps of the East Usambara Mountains of NE Tanzania (Cordeiro 2000). In 2000 the population was estimated at 150-200 in the Amani Nature Reserve, where the majority of the global population is suspected to be found (Cordeiro 2000). The species has been found in other places, including Mt. Nilo and Zirai, with 17 new territories found in the East Usambaras recently (BirdLife International 2015). The total population for this species is currently placed in the band 50-249 individuals, which would roughly equate to 30-200 mature individuals. Despite favouring some edge habitats, it remains vulnerable to forest destruction, especially as it may not cross open spaces easily (Urban et al. 1997), and although the amount of protected forest in the Usambaras has increased there is still heavy pressure on unprotected areas (Evans 1997, Kessy 1998, Doggart et al. 2004). Therefore, the population is inferred to be declining, and as such it warrants listing as Critically Endangered under criterion C2a(ii).
A. sousae was recently rediscovered on the Njesi Plateau in northern Mozambique (Ryan and Spottiswoode 2003). The species was first seen in 1945, and described as a new subspecies (Benson 1945). The expedition that rediscovered it was the first known report of this species since then. The area is undisturbed by humans, and is rarely ever visited (Ryan and Spottiswoode 2003). As such the species may not be threatened by any habitat disturbance, and in the absence of any other known possible threats the population is suspected to be stable. The survey that rediscovered the species found one pair, but also heard unidentified apalis-like calls that may have been this species (Ryan and Spottiswoode 2003). While the lack of many records may suggest the population size is very small, this could also result from the lack of visits to the locality where the species was found. Ryan and Spottiswoode (2003) estimated a total forest area of 12-25km2 at the rediscovery site that may support this species, made up of multiple smaller fragments, which the species can persist in. Additionally, the region contains other possibly suitable areas that have not been investigated (Ryan and Spottiswoode 2003), therefore, it was that the population is likely to be >50 individuals (Ryan and Spottiswoode 2003). While the population size may number more than 50 mature individuals it is unlikely to be very large and so it is suggested that a population size of 50-249 individuals may be appropriate. The species would therefore qualify for listing as Endangered under criterion D.
Comments are invited on these proposed categories and further information would be welcomed.
Benson, C.W. 1945. A new race of Long-billed Forest Warbler from northern Portuguese East Africa. Bulletin of the British Ornithologists’ Club 66: 19.
BirdLife International 2015. Survey success in Tanzania: 17 new territories found for Critically Endangered Long-billed Tailorbird. http://www.birdlife.org/africa/news/survey-success-tanzania-17-new-territories-found-critically-endangered-long-billed
Cordeiro, N. J. 2000. Report on a preliminary census of the Long-billed Tailorbird Orthotomus moreaui in the east Usambara Mountains.
Doggart, N., Kahemela, A. and Mbaga, P. 2004. Gold mining threatens the forests of the Eastern Arc. The Arc Journal 16: 2-3.
Evans, T. D. 1997. Records of birds from the forests of the East Usambara lowlands, Tanzania, August 1994 – February 1995. Scopus 19: 92-108.
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.
Kessy, J. F. 1998. Conservation and utilization of natural resources in the East Usambara forest reserves: conventional views and local perspectives. Wageningen Agricultural University, Wageningen, Netherlands.
Ryan, P. G. and Spottiswoode, C. 2003. Long-billed Tailorbirds (Orthotomus moreaui) rediscovered at Serra Jeci, northern Mozambique. Ostrich 74: 141-145.
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.
Urban, E. K., Fry, C. H. and Keith, S. 1997. The birds of Africa vol. V. Academic Press, London.