Archived 2014 discussion: Woodford’s Rail (Nesoclopeus woodfordi) is being split: list N. woodfordi as Vulnerable and N. immaculatus and N. tertius as Near Threatened?

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. 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 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.

Woodford’s Rail Nesoclopeus woodfordi is being split into N. woodfordi, N. tertius and N. immaculatus, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, N. woodfordi (BirdLife species factsheet) was listed as Near Threatened under criterion B1ab(iii,v), as it was thought to occupy a small range, and to be undergoing a continuing decline owing to habitat degradation and predation by introduced mammals. However, the range was spread over several islands, so it was not considered severely fragmented or restricted to a few locations.

The pre-split species is described as inhabiting damp grassland, grassy thickets, riparian vegetation, abandoned gardens and rarely forest (Dutson 2011). It has been considered potentially susceptible to predation by cats and dogs, exacerbated by incidental capture by hunting dogs and in traps, although it appears to survive, at least locally, close to villages and predators (Webb 1992, K. D. Bishop in litt. 1994). It is said to have increased where damp grasslands are no longer managed and have become overgrown (Dutson 2011). The logging of lowland forest is taking place throughout the range of the pre-split species, although it does not appear to be dependent on forest.

N. woodfordi (as defined following the taxonomic change) is known to be extant on Guadalcanal and may be present on Malaita, Solomon Islands, although the latter population is undescribed (Dutson 2011). An apparent increase in numbers in the coastal north of Guadalcanal was noted around a decade ago (G. Dutson pers. obs. 2002). However, development associated with improved stability following the social unrest of the past c.15 years is expected to facilitate the rapid conversion of grassy habitats. It is therefore suggested that this species be listed as Vulnerable under criterion C2a(ii), as its population may include fewer than 10,000 mature individuals, assumed to form a single subpopulation, which is projected to undergo a continuing decline owing to expected levels of habitat loss and degradation.

N. immaculatus is known to be extant on Santa Isabel and may be extant on Choiseul, Solomon Islands (Dutson 2011). It is reported to be rare in primary forest on Santa Isabel, being more frequent in dense, grassy thickets mixed with primary and secondary forest, including abandoned gardens, especially close to rivers (Webb 1992, G. Dutson pers. obs. 1998). It is said to be locally common, notably along the Garana River where three pairs were heard and one seen along a 2-km path, in 1998 (G. Dutson pers. obs. 1998). It is suggested that this species be listed as Near Threatened under criterion C2a(ii), on the basis that its population is likely to include fewer than 10,000 mature individuals, assumed to form a single subpopulation; however, it is unclear whether the population is in decline, despite the potential threat of predation by introduced mammals, as the species may benefit, at least temporarily, from the clearance of forest.

N. tertius is endemic to Buka and Bougainville (autonomous region of Papua New Guinea). It is abundant in tall grass and shrub thickets, and in 1999 this taxon was reported as common and “thriving” throughout the entire eastern lowlands of Bougainville, probably resulting from a large increase in its population during the seccessionist uprising of 1989-1997 when the island was blockaded, perhaps because the neglect of coastal plantations during this time resulted in an increase in suitable habitat (Hadden 2002). However, it is now inferred to be in decline owing to land-use change and habitat degradation associated with the re-settlement of previously occupied areas on Bougainville. It is suggested that it be listed as Near Threatened under criterion C2a(ii), on the basis that it is likely to have a population of fewer than 10,000 mature individuals, which is inferred to be in decline; however, this flightless species is likely to have two subpopulations, with perhaps over 90% of all mature individuals in the largest subpopulation on Bougainville island.

Comments are invited on these suggested categories and further information is requested, especially on the population estimates, which may be conservative, and the level of habitat fragmentation (the likely percentage of suitable habitat that exists in patches too small to support viable populations).

References:

Dutson, G. (2011) Birds of Melanesia: The Bismarcks, Solomons, Vanuatu and New Caledonia. London, UK: Christopher Helm (Helm Field Guides).

Hadden, D. (2002) Woodford’s rail (Nesoclopeus woodfordi) on Bougainville Island, Papua New Guinea. Notornis 49: 115–121.

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.

Webb, H. P. (1992) Field observations of the birds of Santa Isabel, Solomon Islands. Emu 92: 52–57.

Related posts:

  1. Archived 2014 discussion: Pheasant Pigeon (Otidiphaps nobilis) is being split: list O. insularis as Endangered and O. aruensis as Vulnerable?
  2. Archived 2014 discussion: Maroon-chinned Fruit-dove (Ptilinopus subgularis) is being split: list both P. subgularis and P. mangoliensis as Vulnerable and P. epia as Near Threatened?
  3. Archived 2014 discussion: Javan Frogmouth (Batrachostomus javensis) and Blyth’s Frogmouth (B. affinis) are being lumped as B. javensis: list the newly defined species as Near Threatened?
  4. Archived 2014 discussion: Solomons Hawk-owl (Ninox jacquinoti) is being split: list N. malaitae and N. roseoaxillaris as Vulnerable and N. granti as Near Threatened?
  5. Archived 2012-2013 topics: Tsingy Wood Rail (Canirallus beankaensis): newly recognised and Near Threatened?
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3 Responses to Archived 2014 discussion: Woodford’s Rail (Nesoclopeus woodfordi) is being split: list N. woodfordi as Vulnerable and N. immaculatus and N. tertius as Near Threatened?

  1. Guy Dutson says:

    I am not convinced about splitting these species given the significant inter-taxon variation observed in the field but not exhibited in the very small series of specimens. Although locally common in rank grasslands, this habitat is limited, and population sizes of <10,000 for all three taxa would be my best precautionary estimate. Given the paucity of information on these birds away from one or two birding sites and the largely unknown trends in their habitat, I would list each as NT, aligned with the ecologically similar Roviana Rail.

  2. Joe Taylor says:

    Preliminary proposals

    Based on available information and comments posted above, our preliminary proposals for the 2014 Red List would be to treat:

    N. woodfordi as Near Threatened under criterion C2a(ii)

    N. immaculatus as Near Threatened under criterion C2a(ii)

    N. tertius as Near Threatened under criterion C2a(ii)

    There is now a period for further comments until the final deadline of 31 March, after which recommended categorisations will be put forward to IUCN.

    The final Red List categories will be published on the BirdLife and IUCN websites in mid-2014, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  3. Andy Symes says:

    Recommended categorisations to be put forward to IUCN

    Following further review, there have been no changes to our preliminary proposals for the 2014 Red List status of these species.

    The final categorisations will be published later in 2014, following further checking of information relevant to the assessments by BirdLife and IUCN.

Comments are closed.