Barred Owlet-nightjar (Aegotheles bennettii) is being split: list A. affinis as Data Deficient?

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.

Barred Owlet-nightjar Aegotheles bennettii is being split into A. bennettii and A. affinis (incorporating terborghi), following Dumbacher et al. (2003) and Cleere (2010) and the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, A. bennettii (BirdLife species factsheet) was listed as being of Least Concern, on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.

Very little is known about A. affinis, although it inhabits forest and is thought to be uncommon (Cleere 2010). It has been recorded at up to c.900 m in the Vogelkop Mountains (Rand and Gilliard 1967), to which A. a. affinis appears to be restricted. A. a. terborghi is known from a single specimen, collected in 1964 at c.1,100 m in the Karimui Basin (Diamond 1967).

It may not be possible to derive a reliable estimate of the population trend from available information, although the species is unlikely to be in rapid decline, given rates of forest loss in the vicinity of its known locations. Deforestation rates of c.11-15% over 30 years (1972-2002) have been estimated in the Western Highlands and Southern Highlands of Papua New Guinea (Shearman et al. 2009). Overall forest loss in West Papua has been estimated at 2.4% over 10 years (2000-2010) (Miettinen et al. 2011). The species is thought to have a three-generation trend period of c.16 years, thus it is unlikely that its population trend has approached a decline of 30% over three generations. Based on currently available information it may not be possible to estimate the species’s range size and population size. Few specimens of any owlet-nightjars have been collected in the region between the known localities of affinis and terborghi and future surveys may fill this apparent range gap (Dumbacher et al. 2003).

It is therefore suggested that A. affinis be listed as Data Deficient on the basis that there is insufficient information available for a robust assessment of its threat status against the IUCN Red List criteria.

A. bennettii (as defined following the taxonomic change) is widespread in eastern and north-central New Guinea, where it inhabits forest up to 1,000 m, although rarely above 500 m (Holyoak 2001). Rates of deforestation in the region suggest that the species is not in rapid or moderately rapid decline (a decline approaching 30% over three generations [c.16 years]); overall primary forest loss in mainland lowland Papua New Guinea has been estimated at c.14% from 1972 to 2002, with 7% degraded during that period (Shearman et al. 2009). The species’s known range implies that it does not have a small or moderately small population (approaching as few as 10,000 mature individuals). It is therefore suggested that this species be listed as being of Least Concern, on the basis that it does not approach the thresholds for Vulnerable under any of the IUCN Red List criteria.

Comments are invited on these suggested categories and further information would be welcomed.

References:

Cleere, N. (2010) Nightjars, Potoos, Frogmouths, Oilbird and Owlet-nightjars of the World. Old Basing, UK and Princeton, NJ: WildGuides  and Princeton University Press.

Diamond, J. M. (1967) New Subspecies and Records of Birds from the Karimui Basin, New Guinea. American Museum Novitates 2284.

Dumbacher, J. P., Pratt, T. K. and Fleischer, R. C. (2003) Phylogeny of the owlet-nightjars (Aves: Aegothelidae) based on mitochondrial DNA sequence. Molecular Phylogenetics and Evolution 29: 540-549.

Holyoak, D. T. (2001) Nightjars and their Allies. Oxford, UK: Oxford University Press.

Miettinen, J., Chenghua Shi and Soo Chin Liew (2011) Deforestation rates in insular Southeast Asia between 2000 and 2010. Global Change Biology 17: 2261-2270.

Rand, A. L. and Gilliard, E. T. (1967) Handbook of New Guinea Birds. London, UK: Weidenfeld and Nicolson.

Shearman, P. L., Ash, J., Mackey, B., Bryan, J. E. and Lokes, B. (2009) Forest Conversion and Degradation in Papua New Guinea 1972-2002. Biotropica 41: 379–390.

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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2 Responses to Barred Owlet-nightjar (Aegotheles bennettii) is being split: list A. affinis as Data Deficient?

  1. Joe Taylor says:

    Preliminary proposals

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

    A. bennettii as Least Concern

    A. affinis as Data Deficient

    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.

  2. 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.

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