Archived 2016 topics: Long-billed Tailorbird (Artisornis moreaui) is being split: list A. moreaui as Critically Endangered and A. sousae as Endangered?

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.

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.

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2 Responses to Archived 2016 topics: Long-billed Tailorbird (Artisornis moreaui) is being split: list A. moreaui as Critically Endangered and A. sousae as Endangered?

  1. Jay McEntee says:

    In an August 2011 trip to the Njesi Plateau (funded in part by the Mohamed bin Zayed Species Conservation Fund) with Elia Mulungu, Daniel Portik, and Dalila Sequeira, we discovered that A. (m.) sousae is easily detected and has reasonably high density in Njesi’s forest patches. The density of A. (m.) sousae at the southern end of the Njesi plateau, where we worked, is certainly higher than that of A. moreaui at Amani in the East Usambara. We found at least two areas where territories of vocalizing pairs seemed to be directly adjacent, which is not typical at Amani, where territories are sparse. These observations suggested to me that the population might be of reasonable size (a few hundred individuals) despite the limited extent of forest at Njesi. It should be noted, however, that the forest patches at Njesi occupy an extremely limited elevational range. Changes in the local fire regime or the climate could conceivably threaten the entirety of the forest there. The forest biota has nowhere to move upslope under such changes. A long-overdue note on our findings at Njesi is in development.

  2. James Westrip (BirdLife) says:

    Based on available information, our preliminary proposal for the 2016 Red List would be to conservatively currently adopt the proposed classifications outlined in the initial forum discussion.

    There is now a period for further comments until the final deadline of 28 October, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from those in the initial proposal.

    The final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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