Archived 2020 topic: Yellow-spotted Barbet (Buccanodon duchaillui) is being split: assessment of newly recognised taxa.

Birdlife International factsheet for Yellow-spotted Barbet.

Following a taxonomic reassessment, Yellow-spotted Barbet (Buccanodon duchaillui) has been split into Eastern Yellow-spotted Barbet (B. duchaillui), and Western Yellow-spotted Barbet (B. dowsetti) (see Boesman and Collar, 2019). The newly-split Eastern Yellow-spotted Barbet has a range extending from south-west Nigeria, through the Democratic Republic of Congo to Kenya. Western Yellow-spotted Barbet ranges from Sierra Leone to southern Ghana, but is now absent from Togo and Benin (Boesman and Collar, 2019).

The exact habitat requirements for the newly-split Western Yellow-spotted Barbet have not been investigated, but it is very likely to be similar to Eastern Yellow-spotted Barbet and require lowland and montane forests (del Hoyo et al., 2002). The high forest dependency of these species may make them vulnerable to forest loss. The population size of the pre-split species is unknown, but it is described as relatively common to common (del Hoyo et al., 2002).

The pre-split species was previously listed as Least Concern (BirdLife International 2020). However, following the taxonomic split, new range sizes suggest that both species warrant a thorough reassessment. We have therefore reassessed both species against each criterion here.

Criterion A:

IUCN guidelines stipulate that rates of decline should be measured over the longer of 10 years or 3 generations (IUCN Standards and Petitions Committee, 2019). The generation length for Yellow-spotted Barbet has been recalculated to 3 years (Bird et al., 2020)*, and it is assumed that the generation length for the new Eastern and Western Yellow-spotted Barbets are the same. Therefore, the rates of reduction for these species are calculated over 10 years.

Eastern Yellow-spotted Barbet: The population trend for this species has not been directly estimated, but it is inferred to be declining as a result of ongoing habitat loss (Tracewski et al., 2016; Birdlife International, 2020) The rate of tree cover loss across the post-split range for the Eastern Yellow-spotted barbet between 2000-2018 was 26% (Global Forest Watch, 2020). Assuming that the population declines at the same rate as habitat loss, this equates to a decline rate of 16% over the last 10 years, which is too low to trigger the threatened threshold (≥ 30% reduction over 10 years) under this criterion. Tracewski et al. (2016) also found insignificant rates of deforestation across the pre-split range during their analysis. Eastern Yellow-spotted Barbet may therefore be considered Least Concern under criterion A.

Western Yellow-spotted Barbet: This species may also be threatened by habitat loss. Based on Global Forest Watch data, the range for this species experienced a 19% tree cover loss between 2000-2018. Assuming that the population declines at the same rate as habitat loss, this would equate to a decline rate of 11% over the last 10 years, which is too low to trigger the threatened threshold here. Tracewski et al. (2016) also found insignificant rates of deforestation across the pre-split range during their analysis. Western Yellow-spotted Barbet may therefore be considered Least Concern under criterion A.

Criterion B:

Eastern Yellow-spotted barbet: The Extent of Occurrence (EOO) for the Eastern Yellow-spotted Barbet is calculated to be 4,111,044 km².  This is too high to trigger the threatened threshold (EOO <20,000 km²), and therefore, Eastern Yellow-spotted Barbet may be considered Least Concern under criterion B.

Western Yellow-spotted barbet: The EOO for this newly identified species is calculated to be 524,623 km². This is too high to trigger the threatened threshold (EOO <20,000 km²), and therefore, Western Yellow-spotted Barbet may be considered Least Concern under criterion B.

Criterion C:

The population size for these species have not been estimated, so they cannot be assessed against criterion C.

Criterion D:

The population size for these species have not been estimated, so they cannot be assessed against criterion D.

Criterion E:

To the best of our knowledge, no quantitative analysis has been carried out for these species and so they cannot be assessed against this criterion.

We therefore suggest that both Eastern Yellow-spotted Barbet (B. duchaillui) and Western Yellow-spotted Barbet (B. dowsetti) be listed as Least Concern. We welcome any comments to the proposed listing.

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are relevant to the species’ Red List status and the information requested. By submitting a comment, you confirm that you agree to the Comment Policy.

*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).

An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.

References

Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S., Symes, A., Taylor, J., Şekercioğlu, Ç.H. and Butchart, S.H.M. (2020), Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology. Online first view.

BirdLife International (2020) Species factsheet: Buccanodon duchaillui. Downloaded from http://www.birdlife.org on 12/05/2020

Boesman, P., and Collar, N.J., (2019), Two undescribed species of birds from West Africa, Bulletin of the British Ornithologists’ Club, 139(2) : 147-159

del Hoyo, J.; Elliott, A.; Sargatal, J. 2002. Handbook of the Birds of the World, vol. 7: Jacamars to Woodpeckers. Lynx Edicions, Barcelona, Spain.

Global Forest Watch. 2020. World Resources Institute. http://www.globalforestwatch.org (Accessed 06 May 2020).

IUCN Standards and Petitions Committee. 2019. Guidelines for using the IUCN Red List Categoreis and Criteria. Version 14. http://www.iucnredlist.org/documents/RedListGuidelines.pdf

Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M. 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.

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6 Responses to Archived 2020 topic: Yellow-spotted Barbet (Buccanodon duchaillui) is being split: assessment of newly recognised taxa.

  1. James Bradley says:

    Aside from the fact that “Eastern Yellow-spotted Barbet is doing just fine in East Africa, the split of this bird from the western form is nothing short of fantasy. The evidence is not even convincing, let alone conclusive, and none of it is supported by a genetic analysis.

    The main reason given by Boseman and Collar for splitting these, that western birds sing a song not given by eastern birds, is simply untrue. The flat series of “poop” notes is given commonly by birds in Kenya at least. It has been missed because birders in East Africa are far less focused on forests and far less focused on vocalisations than in West Africa. The complete absence of any other differences at all, from plumage to biometric, in such a distinctive and unique looking bird, should have been a strong indication that the two forms are very, very closely related.

    A poor taxonomic decision in my opinion and I’m shocked it was published.

  2. Red List Team (BirdLife International) says:

    Global Forest Change data on tree cover loss up to 2019 have now been released and made available via Global Forest Watch. Based on these data, over ten years approximately 18% of tree cover with 75% canopy cover was lost from within the range of the Eastern Yellow-spotted Barbet, and approximately 7% of tree cover with 75% canopy cover was lost from within the range of the Western Yellow-spotted Barbet (Global Forest Watch 2020). This does not affect the above assessment under Criterion A.

  3. Ben Phalan says:

    Taxonomic questions aside, I agree that Western Yellow-spotted Barbet (B. dowsetti) should be listed as Least Concern. It is tolerant of a considerable amount of habitat degradation, and while it will have suffered historically from habitat loss, it remains a relatively common species.

  4. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.

    Thank you once again,
    BirdLife Red List Team

  5. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information, our preliminary proposal for the 2020 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.

    There is now a period for further comments until the final deadline in mid-July, 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 those in the initial proposal.

    The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN. The final publication date will be publicised by IUCN here: https://www.iucnredlist.org/assessment/updates

  6. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    The final categorisations for these species have not changed. Eastern Yellow-spotted Barbet and Western Yellow-spotted Barbet are recommended to be listed as Least Concern.

    Many thanks for everyone who contributed to the 2020 GTB Forum process. The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

Comments are closed.