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?

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.

Javan Frogmouth Batrachostomus javensis and Blyth’s Frogmouth B. affinis are being lumped as B. javensis, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, both Javan Frogmouth B. javensis (BirdLife species factsheet) and Blyth’s Frogmouth B. affinis (BirdLife species factsheet) were listed as Least Concern. These species were estimated to have very large ranges, and hence did not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence of less than 20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Their population trends appeared to be stable, and hence these species did not approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). Their population sizes have not been quantified, but they were not believed to approach the thresholds for Vulnerable under the population size criterion (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).

The lumped species, B. javensis, is found in Indochina (including the Thai-Malay Peninsula), Sumatra, Java, Borneo and the western Philippines, where it mainly inhabits lowland evergreen forest, typically mature forest, reaching foothills and lower montane elevations in some areas (Holyoak 2001). In some parts of its range, such as Java, it can be found in tree-rich scrub, and may be able to occupy secondary growth, but luxuriant undergrowth appears to be important (Holyoak 2001). It may qualify as Near Threatened under criteria A2c+3c+4c, as it could be undergoing a moderately rapid population decline (approaching 30% over three generations [c.23 years]), owing to on-going rapid rates of deforestation in lowland areas throughout its range.

Comments on this suggested categorisation are invited and further information would be welcomed.


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

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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7 Responses to 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?

  1. Very tolerant in Lao PDR to forest degradation – considerably more so than Banded Kingfisher and Bay Owl (see comments under those species). If this is typical of its range, then if this frogmouth reaches NT thresholds then really and truly almost every lowland evergreen ‘forest’ species with a wide range in non-Sundaic SE Asia warrants similar listing.

  2. John Pilgrim says:

    It would be good to see the justification for this lump – it doesn’t seem to fit my knowledge of vocalisations. It would be good for someone more informed like James Eaton to comment on that issue…

  3. James Eaton says:

    Firstly I am very surprised these are being relumped – javanesis and affinis have very different vocalisations, I have recorded at least 7 from affinis, and 6 from javanensis, none of which are shared with each other. Sunda Frogmouth could well be more closely related to javanensis given they share a couple of very similar vocalisations.

    All taxa occur in heavily-degraded habitat, including town parks, certain plantations as well as secondary and primary forest. I agree with JWD, if this is NT then every south-east Asian species should be.

  4. Ding Li Yong says:

    Clearly the most resilient frogmouth across South-east Asia, and exhibiting a wide elevational range. The species has been recorded (discontinuously) up to 1200 m asl in parts of Peninsular Malaysia (Gunung Bunga Buah, Bukit Tinggi), and to as low as 20 m asl in the Panti forest reserve. In the logged Panti forest reserve, its the most regularly occurring frogmouth (0 records for Large, and less than 6 for Gould’s in a decade) and i have recorded up to five separate calling individuals in 1.5 km of transect, including very young secondary growth and forest edge. Calling it near-threatened is certainly an overstatement.

  5. Frederic Goes says:

    Not much to added, status in Cambodia fully supports previous comments disadvising listing!

    Conservation: The species is unobtrusive and so more common than records suggest. It is expected to be widespread in the vast extent of suitable habitat in the Cardamom Mountains and parts of the northeast. It is not known to face any specific threats and is not believed to be of conservation concern in Cambodia.

  6. 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:

    B. javensis 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.

  7. 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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