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.
Mountain Serin Serinus estherae is being moved into the genus Chrysocorythus and split into C. estherae and C. mindanensis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, S. estherae (BirdLife species factsheet) was listed as Least Concern on the basis that it was not believed to approach the thresholds for Vulnerable under any criteria. The pre-split species was characterised as rare, scarce and infrequently recorded (Clement 2016). It occurs only at high altitudes: above 1,300m on Java, above 1,900m on Sulawesi, 1,400-3,400m on Sumatra generally at or near the tree line or clearings with scattered shrubs (Clement 2016).
C. estherae has a remarkable distribution, postulated to be relict populations found around scattered mountains in North Sumatra, W and E Java, S and NC Sulawesi. C. mindanensis is known only from a relatively small number of records from Mount Apo and Mount Kitanglad.
C. mindanesis is infrequently recorded, but the elevations at which it occurs are rarely accessed by birdwatchers and there have been few expeditions that have sampled above the treeline. A series of records from Mount Katinglad in 1965 appear to be the most recent specimens; subsequent to this there are few sight records (Peterson et al. 2008), but recently regular sightings have been reported from Mount Dulang-dulang (Birding2asia.com). On Mount Apo there have also been recent sightings, with a flock of 5 observed during a birding trip in 2011 (Hutchinson 2011).
An Extent of Occurrence for the newly split species is likely to be in the order of 3,000km2, with the potential Area of Occupancy very much smaller than this due to the limited area of habitat within the elevational range of the species. Given the remarkable paucity of records from those areas within apparently suitable habitat that people can visit on Mt. Katinglad, it does not appear that it would be abundant anywhere.
Unless further sites are found the species is thought likely to have a small population, which may be restricted to few locations*. However, there is no clear evidence of threats that could be causing a population decline in the species, aside from the potential threat from climate change. Parts of the species’ small range have been developed in the past, notably for hydro power, but this is not believed to be likely to have had a population effect. From minimal information the population is considered to be below 10,000 individuals, which is most likely (though not certain) to be arrange in two subpopulations).
Given the limited distribution and small extent of suitable habitat within that distribution suggesting a small population size, any decline in habitat or population would see the species approach the thresholds for listing as Vulnerable under criterion C2a(i); and B1ab(iii,v), suggesting the species should be considered Near Threatened. Without evidence of a population decline or threats that would infer a decline, then the species should be considered Least Concern.
Equally the population estimate is of poor precision. Were it reasonable to consider that the number of mature individuals approached the threshold for listing as Vulnerable under criterion D1, (<1,000 mature individuals), then this could also lead to the species being listed as Near Threatened.
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).
Birding2Asia.com, undated. Mount Dulang-dulang, Mindanao, Philippines. Web page. Available at http://www.birding2asia.com/W2W/Philippines/Dulang-dulang.html. Accessed 18th October 2016.
Clement, P. (2016). Mountain Serin (Serinus estherae). 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/61325 on 18 October 2016).
Hutchinson, R. 2011. ‘Remote’ Philippines: 27th February – 19th March 2011. birdtourASIA, UK. Available at http://www.birdtourasia.com/pdf%20Reports/Birdtour%20Asia%20Remote%20Philippines%202011.pdf Accessed 18th October 2016.
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.
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.