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.
Scarlet Robin Petroica multicolor is being split into Norfolk Island Robin P. multicolor, Scarlet Robin P. boodang and Pacific Robin P. pusilla, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, P. multicolor (BirdLife species factsheet) was listed as Least Concern, on the basis that it did not approach any thresholds for listing as Vulnerable. However the population on Norfolk Island has been of conservation concern for many years, and is accorded the status Endangered in the Action Plan for Australian Birds 2010 (Garnett et al. 2011). This population has been elevated to species level, thus now requires a global assessment.
The species is known to have declined dramatically during the latter half of the 20th Century, with declines noted initially about 20 years after the introduction of Black Rat in the 1940s (Garnett et al. 2011). Additionally adults have been recorded being predated by feral cats and habitat clearance and fragmentation have exacerbated these problems (Garnett et al. 2011).
The Extent of Occurrence (EOO) is 45 km2, the species being entirely restricted now to Norfolk Island. On the island the area of occurrence (AOO) has been estimated to be 8km2, with the species having been lost from the majority of the island and now largely restricted to the National Park (Garnett et al. 2011). Outside the park the population may have numbered up to 100 pairs in the 1980s (Department of the Environment 2016), but Garnett et al. (2011) reported the absence of birds from recently occupied sites in the first decade of this century. While the population has been mentioned as appearing ‘secure’ since 1997, and this may be the case that inside the national park there has been little change since that time, there also have not been sufficient monitoring efforts anywhere to reliable gauge the trend. The anecdotal evidence provided in Garnett et al. (2011) in fact suggests that there may be an ongoing decline outside the park and the population was classified on a precautionary basis to be declining.
The population was estimated at between 400-500 pairs in 1988 (Robinson 1988 cited in Garnett et al. 2011). This is anticipated to have declined subsequently, hence the population is considered to presently be below 1,000 mature individuals, all in a single subpopulation.
Given the number of threats that the species continues to face, with rats, cats and exotic vegetation all still present on the island (although subject to control measures over part of the island), the assessment made for the 2010 Action Plan is considered to still be appropriate.
Therefore the species is proposed to be listed as Endangered under criterion B1ab(ii,v) + B2ab(ii,iv) on the basis that there are fewer than 5 locations* (given invasive species as the principal threat), the EOO is below 5,000 km2 and the AOO is below 500 km2, and there is a continuing decline in the AOO and in the number of mature individuals.
Additionally the species also qualifies as Endangered under criterion C2a(ii), on the basis that there are fewer than 2,500 mature individuals that occur within a single subpopulation and there is an inferred continuing decline in the population.
The species also warrants listing as Vulnerable under criterion D1, on the basis that the number of mature individuals is below 1,000 and D2, given that AOO is below 20km2 and there is a plausible future threat (both the impact of invasive species or a catastrophic weather event) that could drive the taxon to CR or EX in a very short time.
Were there to be evidence that the population is now stable or increasing throughout the remaining range (inside and outside the National Park), then the species would no longer qualify under the B or C criteria.
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).
Department of the Environment (2016). Petroica multicolor in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Tue, 27 Sep 2016 18:46:33 +1000.
Garnett, S.T. & G.M. Crowley (2000). The Action Plan for Australian Birds 2000. Canberra, ACT: Environment Australia and Birds Australia. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/action/birds2000/index.html.
Garnett, S.T., Szabo, J.K. and Dutson, G. The action plan for Australian Birds 2010. CSIRO Publishing, Collingwood, Victoria 3066, Australia.
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.
IUCN. 2012. Guidelines for Application of IUCN Red List Criteria at Regional and National Levels: Version 4.0. Gland, Switzerland and Cambridge, UK: IUCN.
Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. C. 2010. Quantitative criteria for species delimitation. Ibis 152: 724–746.