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.
Hooded Pitta Pitta sordida is being split into P. sordida, P. novaeguineae and P. rosenbergii, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, P. sordida (BirdLife species factsheet) was listed as Least Concern on the basis that it was not believed to approach any of the thresholds for listing as Vulnerable. The pre-split species was characterised as common and widespread in many areas, and considered to be the most common pitta species where habitat remains within its distribution (Erritzoe 2016). It is tolerant of secondary habitats including commercial plantations and can occur at high density in secondary forest (Erritzoe 2016).
P. novaeguineae (as defined following the taxonomic changes and including P. n. mefoorana and P. n. goodfellowi) is found throughout New Guinea including the W Papuan islands, Aru and Numfor, as well as on Gebe Island in the N. Moluccas. Pitta rosenbergii is found only on the twin islands of Biak -Supiori in Geelvink Bay, NW Papua (Indonesia).
P. rosenbergii is poorly-known, but is suspected to be common in the forests on Biak. The newly calculated EOO for the species is 3,600 km2. Although Biak-Supiori is two islands, the minimal distance between the islands (separated only by a mangrove bordered channel) suggests that it is best to treat the species as being comprised of a single subpopulation. The population is unlikely to be subject to severe fluctuations. However, a slow decline is suspected to be occurring owing to on-going habitat destruction. Forest on Biak is under heavy threat from logging and subsistence farming, but there are relatively large areas of forest remaining, especially in interior Supiori, and the species is assumed to be present in the 110km2 Biak-Utara protected area, which comprises virtually impenetrable forested limestone areas (Dekker et al. 2000, Bishop 1982 in Stattersfield et al. 1998, Wikramanayake et al. 2002). A great deal of the forest clearance on Biak took place during the last century however, with the suggestion that further large scale logging is presently not economically feasible (Wikramanayake et al. 2002). Therefore it is unlikely that declines in the area of habitat are likely to exceed the thresholds for listing under inferred population reduction (category A). In addition, given the apparent tolerance for a degree of habitat modification it is unlikely that the species would qualify for listing under the category B, geographic range size given that there are likely to be more than 10 locations* for the species in terms of habitat destruction, the principle threat.
The population is estimated to number 2,500-9,999 individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals. The density of the species on Biak is thought likely to be higher than that used for the low end of the estimate, hence the number of mature individuals is suggested to be above 2,500. In conjunction with an inferred continuing decline and on the basis that all mature individuals present represent a single subpopulation Pitta rosenbergii is proposed to qualify as Vulnerable under Criterion C2a(ii).
Should there be any evidence that the population size is actually below 2,500 mature individuals then the species would warrant listing as Endangered under the same Criterion.
It is proposed that P. sordida and P. novaeguinae be listed as Least Concern, on the basis that they do not approach any of the thresholds for listing as VU.
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).
Dekker, R.W.R.J., Fuller, R.A., and Baker, G.C. (eds.). (2000). Megapodes. Status Survey and Conservation Action Plan 2000–2004. WPA/BirdLife/SSC Megapode Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK, and the World Pheasant Association, Reading, UK. vii + 39 pp