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.
Black-and-white Monarch Monarcha barbatus is being moved to the genus Symposiachrus and split into Symposiachrus barbatus and S. malaitae, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Monarcha barbatus (BirdLife species factsheet) was listed as Near Threatened under criterion A2c + A3c + A4c, on the basis that it was likely to be experiencing a moderately rapid reduction in population size as logging intensifies within its range. The pre-split species was characterised as fairly common or locally common and occurred in primary and tall secondary forest, and less commonly in secondary growth (Clement 2016). Dutson (2011) considered it rare in flat lowland forest and heavily degraded forest, and rather uncommon overall.
S. barbatus (as defined following the taxonomic change) occurs on the islands of Buka, Bougainville, Shortlands, Choiseul, Isabel, Florida and Guadalcanal in the Solomons. S. malaitae is found only on the island of Malaita, east Solomon Islands.
The newly calculated Extent of Occurrence (EOO) for S. barbatus is 71,108km2, while for S. malaitae the EOO is 6,000km2.
Across the Solomon Islands the rate of forest loss has been considered to be rapid over recent decades, especially so in the lowlands, but the recent rate of deforestation overall is approximately 3-4% over 13 years (the approximate 3 generation length for this species) (Hansen et al. 2013). Degradation of the forest has occurred much more widely with a suggestion that virtually all forests have been accessed for at least a first harvest of round logs (Katavai et al. 2015). Densities of the far commoner and apparently disturbance tolerant White-capped Monarch M. richardsii in secondary forest on New Georgia were only a quarter of those in primary (Buckingham et al. 1995). Unfortunately there are no data on densities for this species in degraded habitat, but as noted above it is rare away from closed canopy hill forest. Consequently this species is likely to have suffered a population declines across its range. It is now known that the majority of the population of S. barbatus occurs in hilly areas, which apparently have not suffered the same degree of degradation as lowland forests. This suggests that the population of the species, while still declining, is thought to be doing so at a moderate rate. The clear preference for primary forest indicates that this decline is likely to remain significant though, and is ongoing.
If the level of habitat degradation and loss is considered to be causing a moderately rapid population decline then S. barbatus may be considered Near Threatened, as it approaches the thresholds for listing as Vulnerable under criterion A2c + A3c + A4c. However, given the apparent reduction in the rate of habitat loss in the past decade on the Solomons, the rate of population decline may be better characterised as slow, and with the population and range size thought to exceed the thresholds for listing under either criteria B or C, the species would be listed as Least Concern. An assessment of population trends is required, and information on the persistence and density of the species in degraded forest.
S. malaitae has a newly calculated EOO of 6,000km2, and is predominately found in primary habitat, though has some tolerance for degraded habitat (G. Dutson in litt. 2016). Malaita has experienced moderate levels of logging and a slow rate of deforestation (Katavai et al. 2015, Hansen et al. 2013). While it is likely that the population size exceeds the thresholds for listing under criteria C, given the extent of habitat degradation it is considered that the population is undergoing a moderately rapid decline, and may approach the thresholds for listing as Vulnerable under criteria A2c + A3c + A4c. As such, it is proposed that Malaita Monarch S. malaitae is listed as Near Threatened.
Comments are invited on these proposed categories and further information would be welcomed.
Clement, P. (2016). Black-and-white Monarch (Monarcha barbatus). 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/59242 on 12 October 2016).
Dutson, G. 2011. Birds of Melanesia: Bismarcks, Solomons, Vanuatu and New Caledonia. Christopher Helm, London.
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 from: earthenginepartners.appspot.com/science-2013-global-forest.
Katovai, E., Edwards, W. and Laurance, W.F. 2015. Dynamics of logging in Solomon Islands: The need for restoration and conservation alternatives. Tropical Conservation Science 8: 718-731.
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.