Archived 2016 topics: Varied Triller (Lalage leucomela) is being split: list L. leucomela as Least Concern and L. conjuncta 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.

Varied Triller Lalage leucomela is being split into L. leucomela and L. conjuncta, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, Lalage leucomela was listed as Least Concern on the basis that it did not approach the threshold for Vulnerable under any criteria. L. leucomela (as now defined following the taxonomic change) is found in a range of forest and woodland habitats, as well as savannah and gardens in northern and eastern Australia, on the island of New Guinea and several associated islands (Taylor 2016a). The species is generally common (Pratt et al. 1987, Flegg and Madge 1995, Coates 1990), but is suspected to be declining in line with habitat destruction (del Hoyo et al. 2005). However, this is not suspected to be large enough to qualify for a threatened category, and so it is proposed that this species be listed as Least Concern.

L. conjuncta is found only on Mussau Island in the St. Matthias group of the Bismark Archipelago, possibly only in the closed forest found on hills (Taylor 2016b). It is currently only known from one specimen and two sets of field observations, and is considered locally common but poorly known (Dutson 2011).

It has an Extent of Occurrence estimated at only c.385 km2, and its habitat is threatened by extensive logging that has occurred, and continues to occur on the island (Taylor 2016b). Its population has not been assessed, but given the species’s very limited range, it is unlikely to be large. Given its restricted range and decline in habitat this species may warrant listing as Endangered under criterion B1ab(i,ii,iii,v). With further information about its likely population size it may also qualify as Endangered under criterion C2a(ii).

 

References:

Coates, B. J. 1990. The birds of Papua New Guinea, 2: passerines. Dove, Alderley, Australia.

del Hoyo, J., Elliott, A. and Christie, D. 2005. Handbook of the Birds of the World, vol. 10: Cuckoo-shrikes to Thrushes. Barcelona, Spain: Lynx Edicions.

Dutson, G. 2011. Birds of Melanesia. Helm, London.

Flegg, J. and Madge, S. 1995. New Holland Publishers Australia, Chatswood, Australia.

Pratt, H. D., Bruner, P. L. and Berrett, D. G. 1987. A field guide to the birds of Hawaii and the tropical Pacific. Princeton University Press, Princeton.

Taylor, B. 2016a. Varied Triller (Lalage leucomela). 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/57891 on 12 September 2016).

Taylor, B. 2016b. St Matthias Triller (Lalage conjuncta). 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/57892 on 12 September 2016).

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.

 

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2 Responses to Archived 2016 topics: Varied Triller (Lalage leucomela) is being split: list L. leucomela as Least Concern and L. conjuncta as Endangered?

  1. Guy Dutson says:

    Not recorded by a recent survey which failed to get to high altitudes (Whitmore (ed) 2015 A Rapid Biodiversity Survey of Papua New Guinea’s Manus and Mussau Islands). It is unlikely to be fragmented across this forested, albeit heavily logged, island, so VU C2aii would be more appropriate, plus VU C1 depending on the rate of forest loss.

  2. James Westrip (BirdLife) says:

    Based on available information, our preliminary proposal for the 2016 Red List would be to list:

    L. leucomela as Least Concern

    L. conjuncta as Vulnerable under criterion C2a(ii).

    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 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.

Comments are closed.