Archived 2014 discussion: Rufous Hornbill (Buceros hydrocorax) is being split: list both B. hydrocorax and B. mindanensis as Vulnerable?

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.

Rufous Hornbill Buceros hydrocorax is being split into B. hydrocorax and B. mindanensis, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, B. hydrocorax (BirdLife species factsheet) was listed as Near Threatened under criteria A2cd+3cd+4cd, on the basis that it was suspected to be undergoing a moderately rapid population decline (approaching 30% over three generations [c.55 years]) owing to on-going habitat loss and persecution.

B. hydrocorax (as defined following this taxonomic change) is found on Luzon and Marinduque, whilst B. mindanensis (incorporating semigaleatus) is found on Balut, Basilan, Biliran, Bohol, Buad, Bucas Calicoan, Dinagat, Leyte, Mindanao, Panaon, Samar, Siargao and Talicud (Kennedy et al. 2000, del Hoyo et al. 2001). They occur largely in primary forest, but may also be found in mature secondary forest and selectively logged forest.

It is suggested that both species be listed as Vulnerable under criteria A2cd+3cd+4cd, on the basis that they are suspected to be undergoing rapid population declines (30-49% over three generations [c.55 years]), owing to the on-going threats stated above.

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


del Hoyo, J., Elliott, A. and Sargatal, J. (2001) Handbook of the birds of the world, Vol 6: Mousebirds to Hornbills. Barcelona, Spain: Lynx Edicions.

Kennedy, R. S., Gonzales, P. C., Dickinson, E. C., Miranda, H. C., Jr. and Fisher, T. H. (2000) A guide to the birds of the Philippines. Oxford: 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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6 Responses to Archived 2014 discussion: Rufous Hornbill (Buceros hydrocorax) is being split: list both B. hydrocorax and B. mindanensis as Vulnerable?

  1. Desmond Allen says:

    sounds reasonable to me

  2. Ivan Sarenas says:

    Ditto, it is the hornbill (mindanensis) that is most likely to be missed by birdwatching tours in the declining forests of Eastern Mindanao and when seen it has always been in minimal numbers.
    Semigaleatus, though is more easily encountered on Samar.

  3. A paper recently completed as part of a DPhil thesis on hornbill evolution (Gonzalez 2012, EGI-Oxford) is waiting to be published. This paper confirms the split into two species of Philippine Buceros (as suggested earlier by Kemp 1995; del Hoyo et al. 2001) based on a comprehensive phenotypic analysis (using the Tobias et al. 2010 criteria) and supported with mtDNA sequence divergence data. Indeed, the threat status will change for both species given their apparent split in distribution and each becoming restricted-ranged species in few remaining patches of preferred evergreen rainforest within their respective range. It is likely to be extirpated in smaller islands (i.e., Panaon, Balut, Talicud) and barely surviving in some islands (i.e., Marinduque, Basilan, Dinagat). Large size and unique nesting habits constrain breeding given the depauperate occurrence of large trees with suitable nest-cavities. Conservation strategies need to address this nesting shortage, coupled with the overall decline of Rufous hornbills. Both are probably influenced by extensively fragmented populations (i.e., South Luzon, South Mindanao), and continued hunting and felling of trees with nest-holes. Recent population studies of hornbills (Gonzalez et al. 2012) in Northeast Luzon show surprisingly low estimates even in fairly intact lowland evergreen forest. Nonetheless, the Sierra Madre mountain range continues to be a key stronghold for B. hydrocorax on Luzon, whereas Samar and West Mindanao are invaluable refuges for B. mindanensis. Indeed, a country-wide population survey for both species would be crucial in the evaluation of their status.

  4. Jayson Ibanez says:

    I support a vulnerable status for the Mindanao hornbill. Although some flocks appear pretty resilient, being able to exist in small isolated fragments like Mt Sinaka KBA (1,000 ha) and the smaller KABIKU watershed (~ 800 ha) in North Cotabato, continued subsistence hunting of this species, felling of remnant dipterocarp forests for agriculture, and petty trade in remote places in Mindanao appears to be further depressing population numbers. Unpublished results of our eagle surveys and habitat assessments show that the species exist in sizable numbers in many KBAs across Mindanao, including the Mt Busa-Kiamba Ranges, Balatukan-Kabalian-Tago Ranges, and the whole of the Eastern Mindanao Corridor. Chats with some Indigenous groups during eagle fieldworks in Mindanao showed socio-cultural affinities with the species similar to what has been identified by Gonzales (2009) in Luzon. Such local ecological knowledge on hornbills by Indigenous peoples can be an effective symbolic capital that can be tapped into to enhance Indigenous engagement to hornbill conservation. Apart from the Sierra Madres, the Cordillera Mountain Ranges might also be another stronghold of B. hydrocorax, particularly the Apayao KBA where eagle surveys between 2012-13 detected sizable flocks of the Luzon hornbill in different sites across the range.

  5. 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. hydrocorax as Vulnerable under criteria A2cd+3cd+4cd

    B. mindanensis as Vulnerable under criteria A2cd+3cd+4cd

    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.

  6. 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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