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.
Golden Bulbul Alophoixus affinis is being moved into genus Thapsinillas and split into T. affinis, T. aurea, T. chloris, T. harterti, T. longirostris, T. lucasi, T. mysticalis and T. platenae, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Golden Bulbul was listed as Least Concern, on the basis that it did not approach the threshold for Vulnerable under any criterion. T. affinis (as now defined following the taxonomic change) and T. mysticalis had previously been split by Handbook of the Birds of the World from all other species involved in this split, and were classed as the Southern Golden Bulbul (see Fishpool and Tobias 2016). T. affinis is found on Seram and Ambon, Indonesia; and T. mysticalis is only found on the island of Buru, Indonesia. Both species are tolerant of even highly degraded forest and may be considered fairly common (Fishpool and Tobias 2016). Neither of these species is thought to approach the threshold for Vulnerable under any criterion, and so it is proposed that they are both listed as Least Concern.
The Northern Golden Bulbul (see Fishpool et al. 2016) part of this split involves T. aurea (on Togian Islands), T. chloris (on Morotai, Halmahera and Bacan), T. harteri (on Banggai Islands), T. longirostris (Sula Islands; the former nominate for Northern Golden Bulbul as per HBW; Fishpool et al. 2016), T. lucasi (found on Obi) and T. platenae (from Sangihe).
All of these species are found in broadleaf evergreen forest, but most are tolerant of at least a degree of degradation, being found in secondary growth, plantations and T. lucasi will occupy forest edges (Fishpool et al. 2016). Therefore, while there are slow rates of forest clearance within the range of these species, the majority are unlikely to be being sufficiently affected by this to warrant listing as Vulnerable. T. chloris, T. harterti, T. longirostri and T. lucasi have all been described as common to abundant, and so it is thought that these species will not approach the threshold for Vulnerable under any criterion and so warrant listing as Least Concern.
T. aurea, found on the Togian Islands of Indonesia, occurs in a range of forested habitats on the islands where it is found, and is tolerant of habitat degradation (see Fishpool et al. 2016). The pre-split species was thought of as relatively common and relatively frequently encountered on Togian and Walea Bahi (Indrawan et al. 2006), and using population density estimates of congeners, and assuming not all of its range is occupied, this species is unlikely to approach the threshold for listing as Vulnerable. However, we request any further information regarding the population structure of this species across the islands within its range to see whether it approaches the threshold for Vulnerable under criterion C2a(i) (<10,000 mature individuals, ≤1,000 mature individuals per sub-population) and so might warrant listing as Near Threatened under this criterion. In the absence of this information, however, it would be proposed that this species be listed as Least Concern.
T. platenae is considered one of the most threatened taxa on Sangihe, with potentially only 50-230 or 70-200 individuals remaining at one location (Gunung Sahendaruman/adjacent Sahengbalira) (Riley 2002, Collar et al. 2013, R. Martin in litt. 2016). This species is found in small groups, possibly representing family groups or ‘breeding units’, of which there may be as few as 20 remaining (R. Martin in litt. 2016), which could mean the effective population size of breeding individuals is as few as 40 mature individuals. Most of Sangihe has been deforested and converted to agriculture and this species is virtually absent from plantations and secondary growth, suggesting an intolerance for habitat degradation (Fishpool et al. 2016). Small scale clearance at the edges of remaining forest continues, and clearings have also been created and maintained on the ridge in a few places for using mist nets to catch bats for food (R. Martin in litt. 2016). Therefore, the population is likely in decline. Given the highly restricted range and very small population size this species likely qualifies as Critically Endangered under criteria B1ab(ii,iii,v);C2a(ii) and possibly under criteria C2a(i);D too if there is further information or comments to support the idea that the effective population size (number of breeding, mature individuals) is ≤50 mature individuals.
Comments are invited on these proposed categories and further information would be welcomed.
Collar, N.J., Eaton, J.A. and Hutchinson, R.O. 2013. Species limits in the Golden Bulbul Alophoixus (Thapsinillas) affinis complex. Forktail 29: 19-24.
Fishpool, L. and Tobias, J. 2016. Southern Golden Bulbul (Thapsinillas affinis). 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/58034 on 7 October 2016).
Fishpool, L., Tobias, J. and Sharpe, C.J. 2016. Northern Golden Bulbul (Thapsinillas longirostris). 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 fromhttp://www.hbw.com/node/58033 on 7 October 2016).
Indrawan, M., Somadikarta, S., Supriatna, J., Bruce, M.D., Sunarto and Djanubudiman, G. 2006. The birds of the Togian islands, central Sulawesi, Indonesia. Forktail 22: 7-22.
Riley, J. 2002. Population sizes and the status of endemic and restricted-range bird species on Sangihe Island, Indonesia. Bird Conservation International 12(1): 53-78.
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.