Tahiti Swiftlet (Collocalia leucophaea) and Marquesan Swiftlet (C. ocista) are being lumped as Aerodramus leucophaeus: list the newly defined species as Least Concern?

The initial deadline for comments on this topic is 10 March 2014, and is therefore later than for most other topics currently under discussion.

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.

Tahiti Swiftlet Collocalia leucophaea and Marquesan Swiftlet C. ocista are being lumped as Aerodramus leucophaeus, following the application of criteria set out by Tobias et al. (2010).

Prior to the taxonomic change, C. leucophaea (BirdLife species factsheet), a resident of moist, forested, rocky valleys on Tahiti in French Polynesia (and probably only a vagrant to other islands) (Chantler and Driessens 2000), was listed as Vulnerable under criteria D1 and D2, on the basis that it has a tiny range, with the breeding population apparently restricted to one small island, where its very small population (fewer than 1,000 mature individuals) is thought to be stable.

This taxon was recorded in five valleys in 1971-1974 (Holyoak and Thibault 1984), and in six valleys (out of 39 visited) during the period 1986-1991 (Monnet et al. 1993). It was apparently never abundant in the 20th century (Holyoak and Thibault 1984); for example, in 1923 it was noted that two local hunters travelled for eight days through the valleys without seeing this species (Beck 1923). In 1997, a new breeding site, with c.30 nests, was found (P. Raust in litt. 1999, C. Blainvillain verbally 2000). A population of c.100 birds is monitored regularly in Papehue valley and appears to be stable (P. Raust in litt. 2007).

The rarity of this taxon is possibly linked to the introduction of the Common Myna Acridotheres tristis (Holyoak and Thibault 1984) (which is known to defend territories, tree hollows and other nesting sites from native birds), and Swamp Harrier Circus approximans (C. Blainvillain verbally 2000). Other introduced species may have a negative impact.

C. ocista (BirdLife species factsheet), a resident of forested areas on the Marquesas Islands in French Polynesia (Chantler and Driessens 2000), 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. It is noted, however, that its population size has not been quantified, although it has been described as common (del Hoyo et al. 1999).

Following the taxonomic change, it is suggested that A. leucophaeus be listed as being of Least Concern, on the basis that it is not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.

Whilst the populations of the two lumped taxa are thought to be stable, any evidence of recent or future declines in their populations and habitats would likely warrant listing of the newly-defined species under a higher threat category.

Comments are invited and further information would be welcomed.

References:

Beck, R. H. (1923) Ornithologie. Bull. Soc. Etud. Océan. Avril: 32-34.

Chantler, P. and Driessens, G. (2000) Swifts: a guide to the swifts and treeswifts of the world. Second Edition. Robertsbridge, U.K.: Pica Press.

del Hoyo, J., Elliott, A. and Sargatal, J. (1999) Handbook of the birds of the world, Vol 5: Barn-owls to Hummingbirds. Barcelona, Spain: Lynx Edicions.

Holyoak, D. T. and Thibault, J.-C. (1984) Contribution à l’étude des oiseaux de Polynésie orientale. Mem. Mus. Natl. Hist. Nat. Ser. A, Zool. 127: 1–209.

Monnet, C., Thibault, J. and Varney, A. (1993) Stability and changes during the twentieth century in the breeding landbirds of Tahiti (Polynesia). Bird Conserv. Int. 3: 261–280.

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 Tahiti Swiftlet (Collocalia leucophaea) and Marquesan Swiftlet (C. ocista) are being lumped as Aerodramus leucophaeus: list the newly defined species as Least Concern?

  1. I read your proposal to lump C. leucophaea and C. ocista as one species Aerodramus leucophaeus.
    I transmitted that proposal to some specialists of birds from French Polynesia such as Jean-Claude Thibault. You will read his comments (in french) under :

    “c’est compliqué les salanganes …. Alice (Cibois) a séquencé du matériel de Atiu (Cook), Tahiti, et des Marquises (Eiao, Nuku Hiva, Ua Huka, Ua Pou et Hiva Oa). Avec les gènes mitochondriaux étudiés, il apparaît clairement qu’il y a eu deux colonisations de la Polynésie. Une première aux Cook avec sawtelli et une seconde dans la Société et aux Marquises. Pour cette seconde colonisation il y a trois lignées, l’une pour Tahiti ( leucophaeus), une seconde pour les Marquises du nord (ocistus ) et une troisième pour les Marquises du sud (gilliardi). La divergence entre ces trois lignées semble avoir été rapide (=branches très courtes dans l’arbre phylogénétique). Il faudrait faire des microsatellites entre Marquises nord et sud pour apprécier s’il y a des échanges, mais nous n’avons pas eu assez de matériel. Il est vrai que les auteurs se sont souvent demandés s’il ne fallait pas regrouper les oiseaux de Tahiti et des Marquises sous la même espèce (à commencer par Holyoak et moi en 1978), mais les différences avec l’ADN sont telles que nous sommes d’avis de reconnaître deux espèces séparées. D’ailleurs, les échanges entre Tahiti et Marquises ont dû être inexistants ou rarissimes une fois les deux archipels colonisés. Le problème se pose au sein des Marquises. Somadikarta a décrit la sous-espèce gilliardi pour le sud (avec Ua Pou) sur la base du critère de tarses emplumés ou non ; mais nous n’avons pas pu confirmer ce critère en examinant les mêmes spécimens à New York. Il a eu le bon oeil en distinguant deux taxons sur un critère morphologique puisque la génétique conclue à la même séparation. Cependant, l’état actuel des analyses ne permet pas de préciser si elle est contemporaine de la colonisation des Marquises par les salanganes ou si elle est plus récente. Provisoirement, on peut dire qu’il y a une espèce (ocistus) avec deux sous-espèces (nominale et gilliardi ).
    Pour les Marquises, il se pose également le problème de la petite population de Fatu Iva dont on ignore l’origine …
    Pour conclure, les résultats génétiques suggèrent de considérer au moins deux taxons, et nous ne voyons pas sur quels critères on pourrait décider de lumper les salanganes de Tahiti et des Marquises. On va essayer de publier ces résultats en 2014.”

    To summarize JC Thibault thinks that the genetic differences are sufficient to keep the distinction between A. leucophaeus and A. ocistus (with 2 subspecies A o ocistus and A o gillardi).

    On an other hand these two species also occur in two different Endemic Bird Areas (Society and Marquesas) separated by more than 2 thousands of km of ocean and genetic exchanges should be inexistant or very rare events.

    Another important reason to have the two species separated is their conservation status. It is astonishing to observe the différences between the number of birds in Tahiti, where they are quite rare with a range restricted to few valleys, and the birds of the Marquesas, where they are the more numerous birds in nearly all the islands fund everywhere at any altitude. There are certainly underlying biological reasons for that not only due to the level of threats by invasive birds.

    I am really worried that if the 2 species are lumped together the Tahitian swiftlet will be considered as not theatened (least concern) which is obviously NOT the case.

    This is why I suggest not to lump these 2 species.

  2. Andy Symes says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2014 Red List would be to treat the newly-defined Polynesian Swiftlet Aerodramus leucophaeus as Least Concern.

    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 categorisation to be put forward to IUCN

    Following further review, there has been no change to our preliminary proposals for the 2014 Red List status of this species.

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

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