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.
Ivory-breasted Pitta Pitta maxima is being split into P. maxima and P. morataiensis, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, Pitta maxima (BirdLife species factsheet) was listed as Least Concern on the basis that it was not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appeared to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The pre-split species was characterised as being locally common, although the global population size had not been quantified, but had a high dependency on forest.
Pitta morotaiensis is restricted to the island of Morotai, north of Halmahera in the North Moluccas. The newly calculated EOO for the species is 2580 km2, and there is assumed to be a single subpopulation. The pre-split species occurs at relatively high densities, 18.2-37.7 inds/km2 (Poulsen et al. 1999) so it is suspected that the number of mature individuals falls within the band 6,667 – 13,333, rounded to 6,000-15,000 mature individuals (assuming an occupancy of 20%). Much of Morotai lies within the elevational range given for the pre-split species (sea level to 800 m) and the island still holds a considerable area of primary forest, indicating that this may be a conservative estimate. Forest loss on the island is ongoing, with approximately 8% loss of forest with over 30% canopy cover between 2000 and 2014 (using data from Hansen et al. 2013), although Vetter (2009) indicated that the rate of loss between 1990-2003 was considerably higher (estimates of total rate of loss for Morotai were not presented as only half of the island was included in the study). The generation length for the species is estimated to be 4.2 years.
On this basis it is proposed that the species be listed as Near Threatened as it appears to approach the thresholds for Vulnerable under Criterion C2a(ii). If there was evidence that the population is actually below 10,000 mature individuals then P. morotaiensis would warrant listing as Vulnerable under the same Criterion.
Should there be evidence that the rate of population decline is equal to or exceeds 30% over three generations then Pitta morotaiensis would qualify as Vulnerable under Criterion A2c+3c+4c.
Note that the species is not considered to approach the thresholds for listing under the geographic range categories as there is no evidence of extreme population fluctuation and the number of locations* (framed in terms of the extent of habitat loss as the principle threat) is considered to exceed 10.
Following the split Pitta maxima is still considered not to approach the thresholds for Vulnerable, with a newly calculated EOO of 62,000 km2.
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).
IUCN (2001) IUCN Red List Categories and Criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.
Poulsen, M. K., F.R. Lambert dan Y. Cahyadin. 1999. Evaluasi Terhadap Usulan Taman Nasional Lalobata dan Aketajawe (Dalam Konteks Prioritas Konservasi Keanekaragaman Hayati di Halmahera). Bird Life International Indonesia Program Bekerjasama Dengan Departemen Kehutanan. Bogor.
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.
Vetter, J. (2009) Impacts of Deforestation on the Conservation Status of Endemic Birds in the North Maluku Endemic Bird Area from 1990-2003. MSc Project. Durham, NC: Duke University.