The initial deadline for comments on this topic is 28 April 2014, and therefore later than for most other topics currently under discussion.
This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for non-passerines
Lynx Edicions and BirdLife International will soon publish 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.
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 1 of the checklist (for non-passerines) will begin to be incorporated into the 2014 Red List update, with the remainder, and those for passerines (which will appear in volume 2 of the checklist), 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.
Grey-green Fruit-dove Ptilinopus purpuratus is being split into P. purpuratus (Grey-green Fruit-dove) and P. chrysogaster (Raiatea Fruit-dove), following the application of criteria set out by Tobias et al. (2010).
Prior to the taxonomic change, P. purpuratus (BirdLife species factsheet) was listed as being of Least Concern, on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.
The newly-defined P. purpuratus is endemic to French Polynesia, where it occurs on Tahiti (nominate purpuratus) and Moorea (P. p. frater). Historically it was reportedly very common, but is now generally less abundant (Gibbs et al. 2001). It occurs in lowland forest to 600 m on Moorea and 800-900 m, perhaps 1,000 m on Tahiti, and is not found in montane forest, coconut plantations or reef islets (Gibbs et al. 2001). It reportedly uses primary and secondary forest, agricultural land and gardens (Spotswood 2011), and its Extent of Occurrence has been estimated at c.1,200 km2.
Both Moorea and Tahiti are now thought to hold populations of a few thousand individuals (J. C. Thibault pers comm in Spotswood 2011). In 1973 there were an estimated 5,000 – 6,000 birds on Moorea with 2-3 birds per hectare in some valleys (Gibbs et al. 2001, Spotswood 2011). It was reportedly very abundant in 1907, but is thought to have declined since 1900, though no systematic surveys have quantified changes and a survey of valleys in Tahiti suggested that populations remained stable in the 20th century (Monnet et al. 1993 in Spotswood 2011).
Mist netting data suggest that it is most common at two sites on Moorea located in low elevation native rainforests, a habitat that is now rare on most of the Society Islands (Spotswood 2011). Non-native fruit are present in at least half the diet of the fruit-dove, however, the low numbers of individuals in forest types not dominated by native species suggests that it may be dependent on plant communities containing native and endemic plants in spite of the apparent generalist nature of its diet (Spotswood 2011). Further potential threats include predation by Swamp Harrier Circus approximans and feral cats, competition with non-native Red-vented Bulbul Pycnonotus cafer and Common Myna Acridotheres tristis, and predation of eggs by rats.
Although its population may be in slow decline, it is proposed that P. purpuratus be listed as Least Concern since declines are unlikely to be c.25% or higher over three generations (ten years), and although it has a small range it is not thought to be very or severely fragmented or restricted to a few locations. The current population size is uncertain but may number fewer than 10,000 mature individuals, however both subpopulations are thought to contain several thousand individuals therefore the thresholds for classification as Vulnerable under criterion C2 are unlikely to be approached.
P. chrysogaster occurs on Huahine, Raiatea, Tahaa, Bora Bora and Maupiti in the Leeward Islands of French Polynesia. It is poorly-known but occurs in lowland forest to an elevation of 450 m on Raiatea (Gibbs et al. 2001). On Huahine (75 km2) and Raiatea (168 km2) it was described as reasonably common and occurring at densities of 6-7 per hectare in some parts of Raiatea. On Tahaa (90 km2), Bora Bora (29 km2) and Maupiti (11 km2) it is uncommon, with populations in 1973 estimated at 500, 50 and 100 birds respectively (Gibbs et al. 2001). Current population sizes on these islands are unknown, and there appear to be no estimates for Huahine and Raiatea. The total population is presumed to be greater than 1,000 mature individuals, and may lie within the band 1,000-2,499 mature individuals.
It is proposed that the species be listed as Near Threatened (approaching the threshold for classification as Vulnerable under criterion D1) as, given the uncertainty over the population size, there is a reasonable possibility it may approach as few as 1,000 mature individuals. The population trend is unknown but assumed to be stable in the absence of evidence for any significant threats.
If the total population is not thought to approach as few as 1,000 mature individuals and there are no significant threats likely to be driving declines, the species may instead warrant listing as Least Concern. If there is evidence to infer or predict a continuing decline in population, range size or quality or extent of habitat, it may instead warrant a higher threat category.
Comments are invited on the proposed classifications and further information would be welcomed.
Gibbs, D.; Barnes, E.; Cox, J. 2001. Pigeons and doves: a guide to the pigeons and doves of the world. Pica Press, Robertsbridge, U.K.
Spotswood, E. N. 2011. Interactions of Avian Frugivores and Invasive Trees in French Polynesia. PhD thesis, University of California, Berkeley. http://escholarship.org/uc/item/8qv4x99z#page-3
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.