Archived 2016 topics: Guadalcanal Thicketbird (Megalurus whitneyi) is being split: list M. whitneyi as Near Threatened and M. turipavae as Vulnerable?

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.

Guadalcanal Thicketbird Megalurus whitneyi is being split into M. whitneyi and M. turipavae, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, M. whitneyi was listed as Near Threatened under criteria A2e+3e+4e;C1, on the basis that it was likely to have a moderately small population which is probably declining due to the presence of invasive predators (BirdLife International 2016). M. whitneyi (as defined now following the taxonomic change) is found only on Santo, Vanuatu in montane forest with a dense undergrowth (Dutson 2011). It is terrestrial and as such may be at risk from invasive predators such as cats and rats (del Hoyo et al. 2006, Dutson 2011). It is described as ‘fairly common’ but the population size and trend have not been quantified, and may be difficult to accurately quantify because of the species’s shy nature (del Hoyo et al. 2006). However, given its restricted range the population size is unlikely to be large and it is likely to be undergoing a moderate decline due to the presence of invasive predators. Therefore, it is proposed that it be listed as Near Threatened under criteria A2e+3e+4e;C1.

M. turipavae is endemic to Guadalcanal, Solomon Islands, and is found in upper montane forest, with both dense and sparse undergrowth (Dutson 2011). It is known from only 3 records, but is likely to be more widespread than sightings suggest as it is difficult to record due to its shy nature (del Hoyo et al. 2006). However, its restricted range and the lack of records do suggest that the population is likely to be relatively small (<10,000 mature individuals). It is particularly threatened by introduced predators such as cats and rats due to its terrestrial behaviour (del Hoyo et al. 2006, Dutson 2011), and so is thought to be declining. Therefore, the species likely warrants listing as Vulnerable at least under criterion C2a(ii).

Comments are invited on these proposed categories and further information would be welcomed.

References:

BirdLife International 2016. Species factsheet: Megalurulus whitneyi. Downloaded from http://www.birdlife.org on 23/09/2016.

del Hoyo, J., Elliott, A. and Christie, D. 2006. Handbook of the Birds of the World, vol. 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona, Spain.

Dutson, G. 2011. Birds of Melanesia: Bismarcks, Solomons, Vanuatu and New Caledonia. Christopher Helm, London.

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: Guadalcanal Thicketbird (Megalurus whitneyi) is being split: list M. whitneyi as Near Threatened and M. turipavae as Vulnerable?

  1. Guy Dutson says:

    Predators are a risk to M. whitneyi but there is no evidence of any decline and Masibalavu & Dutson 2006 found an ecologically similar species, the Long-legged Warbler, to co-exist (and breed successfully) with rats and mongoose. Stephen Totterman (in litt 2010) camped for 21 nights in the species’ range and assessed it as “common from 800 to perhaps 1500 m, and regular at 500 m at Butmas”. I suggest LC for M. whitneyi.

    M. turipavae is much rarer – there might be an additional couple of records (ask Chris Filardi and Markus Lagerqvist) to the three records noted in my book. As with whitneyi, I think that predators area risk but with no evidence of a decline (and no significant risk to the habitat), I would categorise the species under D.

  2. James Westrip (BirdLife) says:

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

    M. whitneyi as Least Concern.

    M. turipavae as Near Threatened under criterion D1 because in the absence of evidence for any decline the population is assumed to be stable, yet the scarcity of the species also suggests that it may approach the threshold for Vulnerable under this criterion.

    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.

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