Archived 2016 topics: White-browed Shortwing (Brachypteryx montana) is being split: could B. floris be considered Near Threatened?

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.

White-browed Shortwing Brachypterys montana is being split into B. montana, B. cruralis, B. sinensis, B. goodfellowi, B. poliogyna, B erythrogyna, B. saturata and B. floris, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, B. montana (BirdLife species factsheet) was listed as Least Concern on the basis that it did not approach the thresholds for listing as Vulnerable under any crtieria.

The pre-split species was characterised as generally scarce, uncommon or locally common but easily overlooked (Clement and Rose 2015), and undoubtedly under recorded. It had a very large range, but was typically found in dense, moist montane forest throughout.

B. montana (as defined following the taxonomic change) is found in in the mountains of Java only. B. cruralis is found from in the central and eastern Himalayas to NW Thailand, Laos and Vietnam, while B. sinensis occurs in SE China and B. goodfellowi is found in the mountains of Taiwan. B. polygyna is distributed thoughout the Philippines and B. erythrogyna occurs in the mountains of north and central Borneo. B. saturata is found in the mountains of Sumatra and B. floris is restricted to the mountains of Flores in the Lesser Sundas.

B. floris is restricted to montane forest within an approximate extent of occurrence in the order of 15,000km2. However there remains considerable habitat within the altitudinal range of the species and there is no evidence that the population is declining. Consequently it is proposed to be listed as Least Concern. However there are only records from very few localities, and confirmation of the species presence across the other suitable areas of upland Flores would exclude the possibility that the population may approach the Vulnerable threshold and potentially be eligible for listing as Near Threatened.

The new nominate B. montana Javan Shortwing is restricted to montane forest above about 1,200 m in western and central Java (eBird 2016, GBIF 2016). The extent of occurrence is considerably in excess of the thresholds for listing under the geographic range criterion and there remains considerable suitable habitat within the altitudinal range of the species. Within Gunung Gede-Pangrango National Park the species is frequently encountered and appears relatively common, which would suggest that the population was considerably more than 10,000 mature individuals. It is only rarely recorded in the cage bird trade and is not targeted by trappers: 3 individuals were noted out of nearly 20,000 birds recorded in a survey of the largest markets in Jakarta in 2014 (Chng et al. 2015). In the absence of any evidence of a decline in the population of the species it is proposed that the species is listed as Least Concern.

B. saturata Sumatran Shortwing is restricted to montane forest above about 1,200 m in Sumatra. The extent of occurrence is considerably in excess of the thresholds for listing under the geographic range criterion and there remains considerable suitable habitat within the altitudinal range of the species. Within Gunung Kerinci National Park the species is frequently encountered and appears relatively common, which would suggest that the population was considerably more than 10,000 mature individuals. In the absence of any evidence of a decline in the population of the species this is also proposed as Least Concern.

Bornean Shortwing B. erythrogyna has been described as a scarce montane resident, occurring from 885-3,600m altitude in montane forest but also above the tree line on bare rock and has been trapped in rice padi (Mann 2008). This habitat has, to date, suffered the least conversion of any on Borneo and the species is therefore not suspected of having declined at a rate approaching the thresholds for Vulnerable. The range is greatly in excess of the thresholds for criterion B, and the status of the species is assessed as being likely similar to Bornean Stubtail Urosphena whiteheadi, currently considered of Least Concern. Consequently B. erythrogyna is suggested to also be Least Concern.

Similarly Philippine Shortwing B. poliogyna does not approach the thresholds for listing under geographic range, there remains a large area of habitat within the altitudinal range of the species (over 1,000 m [Dickinson et al. 1991]) and is consequently suggested to be Least Concern.

B. cruralis, B. sinensis and B. goodfellowi all have very large ranges within which the species occurs within high altitude habitat that is not been suffering high levels of habitat loss. Consequently they are proposed to be listed as Least Concern.

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

References:

Chng, S. C. L., Eaton, J. A., Krishnasamy, K., Shepherd, C. R. & Nijman, V. 2015. In the market for extinction: an inventory of Jakarta’s bird markets. Petaling Jaya, Selangor, Malaysia: TRAFFIC.

eBird. 2016. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, New York. Available: http://www.ebird.org. (Accessed: 6th October 2016).

GBIF Secretariat: GBIF Backbone Taxonomy. doi:10.15468/39omei
Accessed via http://www.gbif.org/species/5230996 on 2016-10-06

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.

This entry was posted in Archive, Asia, Taxonomy and tagged , , , . Bookmark the permalink.

3 Responses to Archived 2016 topics: White-browed Shortwing (Brachypteryx montana) is being split: could B. floris be considered Near Threatened?

  1. Des Allen says:

    probably correct for poliogyna of the Phils, though there appear to be other very distinct song types indicating further cryptic species

  2. James Eaton says:

    Given floris’s preference for secondary, degraded habitat, I would say this is a fair assessment.

  3. 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.

Comments are closed.