Archived 2016 topics: Golden Whistler (Pachycephala pectoralis) is being split: list P. feminina as Near Threatened?

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.

Golden Whistler Pachycephala pectoralis is being split into P. pectoralis, P. orioloides, P. feminina, P. vitiensis, P. mentalis, and P. par, based partly on the application of criteria set out by Tobias et al. (2010), but significantly on a general commonality of characters, with usually no attempt to apply the Tobias criteria owing to incomplete character constancy.

Prior to this taxonomic change, Pachycephala pectoralis (BirdLife species factsheet) was listed as Least Concern, on the basis that it did not approach the thresholds for listing as Vulnerable under any criteria. The pre-split species was considered common, but across the very extensive range there were considerable differences in habitat associations and abundance (Boles 2016).

P. pectoralis (as defined following the taxonomic changes) comprises 31 subspecies ranging from the Banggai and Sula Islands (Sulawesi), through the Moluccas, Timor, WC New Guinea, the Bismark and Louisiade Archipelagos, Santa Cruz Islands, Vanuatu, the Loyalty Islands, Australia, Tasmania, Lord Howe and Norfolk Island. P. orioloides occurs throughout the Solomon Islands apart from Rennell. P. vitiensis is found throughout Fiji and P. mentalis is found throughout the north Moluccas. These four newly defined species are all considered not to approach the thresholds for listing as Vulnerable under any criteria, hence it is suggested they be listed as Least Concern.

P. feminina, Rennell Whistler, is restricted to Rennell Island in the S Solomon Islands and has a newly calculated extent of occurrence (EOO) of 1,340km2. Rennell Island is currently suffering a significant rate of habitat loss (Hansen et al. 2013) and this species is noted to be one of the least common of the Rennell endemics, and seems to occur at lower densities than other members of the complex of species (Dutson in litt. 2016). The population is estimated to number 10,000-19,999 individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners 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 6,667-13,333 mature individuals, rounded here to 6,000-15,000 mature individuals.

It is suggested that P. feminina is listed as Near Threatened, on the basis that it approaches the thresholds for listing as Vulnerable under criterion C2a(ii), as it has a small population considered likely to be suffering an ongoing decline. If there is evidence that the population numbers considerably more individuals than estimated here, or there is evidence that the population is stable, then the species may be classified as Least Concern.

P. par, Banda Sea Whistler, is found on Romang Island and Leti and Moa in the Leti Archipelago, in the east Lesser Sundas. The newly calculated EOO for the species is 3900km2, however an effective ‘maximum area of occupancy’ derived from the total area of the three islands on which the species occurs is approximately 600km2. Unlike much of the rest of the ‘Golden Whistler’ species complex, this taxon is described as relatively elusive and present in primary and secondary forest and gardens, rather than disturbed habitats (Trainor and Verbelen 2013). On Romang the species comprised only about 10% of the whistlers observed (the rest being Wallacean Whistler P. arctitorquis), while on Leti a single individual was recorded in two days (survey effort compromised by the surveyor contracting malaria) (Trainor and Verbelen 2013). Recent bird tour groups have seen the species relatively easily however (e.g. BirdtourASIA 2013).

Romang has a high proportion of forested land, while Leti and Moa are largely covered by arid grassland, considered unsuitable for the species. Despite this, the population is considered unlikely to approach the thresholds for listing under criterion D, given that there remains a large area of suitable habitat on Romang.

It is suggested that P. par is listed as Least Concern but further information to help with clarifying the population size is needed. If the total population were likely close to 1,000 mature individuals then the species may warrant listing as Near Threatened under criterion D1.

P. teysmanni, Salayar Whistler, is found only on the island of Salayar off south Sulawesi. The newly calculated EOO for the species is 829km2. Dutson (1995) found the species to be common in secondary and disturbed habitats during only a short visit to Salayar. Given the species’ tolerance of disturbance, there is unlikely to be any decline in population or habitat extent available to the species. It is also thought that the population is considerably higher than the thresholds for consideration of criterion D, despite the very small range of the species.

It is suggested that this species should be also be listed as Least Concern, but as above further information to assist with clarifying the population size would be very helpful. If the total population were likely close to 1,000 mature individuals then the species may warrant listing as Near Threatened under criterion D1.

References:

BirdtourASIA 2013. ‘Banda Sea Cruise 14th October – 2nd November 2013. Leader Frank Lambert. http://www.birdtourasia.com/pdf%20Reports/Birdtour%20Asia%20Banda%20Sea%20Cruise%202013.pdf. Accessed 29th September 2016.

Boles, W. (2016). Golden Whistler (Pachycephala pectoralis). 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/59355 on 29 September 2016).

Dutson, G. 1995. The birds of Salayar and the Flores Sea Islands. Kukila 7(2): 129-141.

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. 2010. Quantitative criteria for species delimitation. Ibis 152: 724–746.

 

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3 Responses to Archived 2016 topics: Golden Whistler (Pachycephala pectoralis) is being split: list P. feminina as Near Threatened?

  1. Guy Dutson says:

    Notably less common in secondary habitats: a total of 5 (mostly singing birds: song audible for about 100 m) in mixed secondary with some patches of old-growth forest in 17 hours in 1998, compared to 29 in mostly old-growth forest in 14 hours. Currently large areas being logged on Rennell. Population size possibly too high for C2aii.

  2. Rob Martin (BirdLife International) says:

    Given the attention drawn to the rate of logging on Rennell and the considerable difference in densities noted in secondary versus primary habitat it is considered that the species may be undergoing a decline that approaches the thresholds for listing under criterion A.

  3. Rob Martin (BirdLife International) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2016 Red List would be to list Rennell Whistler as Near Threatened under criteria A2c + A3c + A4c; C2a(ii).

    There is now a period for further comments until the final deadline of 28 October, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.

    The final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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