Archived 2016 topics: Kerala Laughingthrush (Strophocincla fairbanki) is being moved to genus Trochalopteron and split: list T. fairbanki as Near Threatened and T. meridionale 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.

Kerala Laughingthrush Strophocincla fairbanki is being moved to genus Trochalopteron and split into T. fairbanki and T. meridionale, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, Kerala Laughingthrush was listed as Near Threatened under criterion B1ab(i,ii,iii,iv,v), on the basis that it had a ‘small global range, and is likely to be declining as a result of habitat loss. However, it is able to persist in some degraded habitats, suggesting that it may not be at imminent risk’ (BirdLife International 2016). Trochalopteron fairbanki (as now defined following the taxonomic change) is found in the Western Ghats south of the Palakkad gap until the Shenogottah (=Achenkovil) gap (see Praveen J. and Nameer 2012). T. meridionale is found further south of this in the Agasthyamalai hills (Praveen J. and Nameer 2012). The pre-split species was found in a range of habitats and can tolerate habitat degradation, occurring in plantations, scrub, secondary forest, gardens, and forest edge (Collar and Robson 2016).

Both species are range restricted with possible Extents of Occurrence <5,000km2 (Praveen J. and Nameer 2016), pending Minimum Convex Polygon analyses. There is forest destruction occurring within both species’s ranges (see Hansen et al. 2013), which may be reducing the area/quality of available habitat; though their tolerance for habitat degradation may mean that any population declines will be slow. They may not qualify as threatened under criterion B1, though, as it is not certain to what extent each species may be severely fragmented rather than just fragmented (see IUCN 2001, 2012) and rates of forest loss suggest both species may be found at >10 locations*.

The population size of both species has not been quantified, but the species has been described as locally ‘fairly common’ (del Hoyo et al. 2007). Based on known records and range size the population size of T. fairbanki likely exceeds 10,000 mature individuals and would not approach the threshold for Vulnerable under criterion C. The population size of T. meridionale may be estimated at 2,500-9,999 mature individuals, which fits with population density estimates for congeners and an assumption that only a proportion of its range is occupied. Therefore, T. meridionale may qualify as Vulnerable under criterion C2a(ii). In the absence of any further information regarding the degree of fragmentation of the population of T. fairbanki, it is suggested that this species be listed as Near Threatened under criterion B1ab(iii,v).

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

*Note that the term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat (IUCN 2001, 2012).

References:

Collar, N. and Robson, C. 2016. Kerala Laughingthrush (Strophocincla fairbanki). 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/59617 on 12 October 2016).

del Hoyo, J., Elliott, A. and Christie, D. 2007. Handbook of the Birds of the World, vol. 12: Picathartes to Tits and Chickadees. Lynx Edicions, Barcelona, Spain.

Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. Chini, C. O. Justice, and J. R. G. Townshend. 2013. High-Resolution Global Maps of 21st-Century Forest Cover Change. Science 342: 850–53. Data available on-line from: http://earthenginepartners.appspot.com/science-2013-global-forest. Accessed through Global Forest Watch on 10th October 2016. www.globalforestwatch.org

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.

Praveen J. and Nameer, P.O. 2012. Strophocincla Laughingthrushes of South India: a case for allopatric speciation and impact on their conservation. J. Bombay Nat. Hist. Soc. 109: 46-52.

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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3 Responses to Archived 2016 topics: Kerala Laughingthrush (Strophocincla fairbanki) is being moved to genus Trochalopteron and split: list T. fairbanki as Near Threatened and T. meridionale as Vulnerable?

  1. James Westrip (BirdLife) says:

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

  2. Vivek Chandran A says:

    A study was done on the territoriality of T.meridionale (Strophocincla fairbanki meridionalis) in 2010-11 (Journal of the Bombay Natural History Society, 110(2), Pg 142-146, May-Aug 2013) by myself and Praveen J. Breeding territories were not recorded in vast swathes of Ochlandra cover in its habitat. Booming tourism, man-made fires and illegal felling of trees were identified as serious threats faced by the taxon. The average breeding territory size of the taxon was estimated to be around 2 hectares with an average distance of 66 metres between the adjacent territories. Based on this information, and known Extend Of Occurrence of the taxon, an attempt was made to arrive at the population size of the taxon which provided a global population estimate of 5806 pairs.The population estimate was however edited out of the published paper. Nevertheless, it seems relevant to be considered for assigning the IUCN status now.

  3. Praveen J says:

    T. meridionale

    As per Praveen & Nameer (2012), AOO of the species is < 304 sq.km – definitely below 500 sq.km. threshold for Endangered. This is still an upper bound as it is calculated only be eliminating unsuitable altitudes in its range. Unsuitable habitat (Large Ochlandra breaks, Rocky areas, Grasslands without sholas) removal will further reduce this value. Hence it clearly qualifies for Endanged under B2abiii.

    EOO has not been calculated using Joppa et al. (2015), hence the recommendations from Praveen & Nameer (2012) based on EOO cannot be directly used here. However, if we redo it using Joppa et al. (2015), it will still fall well under 5000 sq.km. as the range is compact and not spread with unsuitable habitats between them. Hence, qualifies as Endangered under B1abiii also.

    5806 pairs estimated uses the 302 sq.km. for the population estimate.
    https://www.researchgate.net/publication/265515950_Territoriality_in_Kerala_Laughingthrush_Strophocincla_fairbanki_meridionalis
    Hence, when unsuitable habitats are also removed, it will further reduce. So, this population estimate is a strong upper bound and the likely population size will be lower than this.

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