Shelley’s Eagle-owl (Bubo shelleyi): revise global status?

A rare and poorly known species, Shelley’s Eagle-owl (Bubo shelleyi) is currently listed as Near Threatened (see BirdLife International 2018). It is known only from scattered locations from Sierra Leone, Liberia, Côte d’Ivoire, Ghana (where it could now be extirpated), Nigeria, Cameroon south to Gabon and across through Congo and the Democratic Republic of the Congo (see Grimes 1987, Borrow and Demey 2001, Dowsett-Lemaire and Dowsett 2009, 2014, Holt et al. 2018).

As one of the most poorly known African owls its ecology and behaviour are mainly unknown, but it has been recorded in forest habitats including at the forest edge, gallery forest and at the edge of forest clearings (Fry et al. 1988, see also König and Weick 2008, and Borrow and Demey 2010 per Holt et al. 2018). Shelley’s Eagle-owl is the largest forest owl in Africa, and so likely requires large areas of suitable habitat. This means that the overall population size is potentially very small, and the key threat to the species is assumed to be deforestation. Based on these fears it was suggested that this species may warrant a revision of Red List status (H. Rainey in litt. 2018), and so we have reassessed the species here against all criteria.

 

Criterion A – Tracewski et al. (2016) estimated an annual decline in forest cover within this species’s range to be c.0.2% between 2000 and 2012. This would roughly equate to a decline of 6.4% over three generations (c.35 years). Therefore, the species may be inferred to be in decline. However, the suspected rate of decline based on forest loss is considerably lower than the threshold for Vulnerable. Thus, the species would not warrant listing under this criterion.

 

Criterion B – The species’s range is too large to warrant listing under this criterion.

 

Criterion C – The species’s population is currently considered to be fewer than 10,000 individuals due to its requirements for large areas of suitable habitat. It has therefore been placed in the range 2,500-9,999 individuals, roughly equating to 1,667-6,666 mature individuals, which has been rounded to 1,500-7,000 mature individuals. Thus, Shelley’s Eagle-owl at least meets the population size threshold for Vulnerable, and potentially Endangered too; although further sub-conditions need to be met to warrant listing as such.

While we can infer a continuing decline due to habitat loss, the rate of decline is uncertain (we can only suspect a rate of decline based on habitat loss) so it cannot be accurately assessed against Criterion C1 and even so, the rate of forest loss presented in Tracewski et al. (2016) is below the threshold for Vulnerable anyway. Additionally, the species is not thought to undergo extreme fluctuations so does not warrant listing under Criterion C2b. The species is also split into multiple sub-populations and so does not warrant listing under Criterion C2a(ii). However, because it is split into multiple sub-populations it is possible that the largest sub-population contains <1,000 mature individuals, although it is unlikely that it would contain <250 mature individuals. Therefore, it could warrant listing as Vulnerable under Criterion C2a(i).

 

Criterion D – With a population size range of 1,500-7,000 mature individuals the species would not meet the threshold for listing as Vulnerable under this criterion.

 

Criterion E – To the best of our knowledge, there has been no quantitative analysis of extinction risk conducted for this species. Therefore, it cannot be assessed against this criterion.

 

Therefore, we could tentatively proposed to uplist Shelley’s Eagle-owl to Vulnerable under criterion C2a(i), although we request any comments regarding this proposed listing. Please note though 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 about the proposed listing.

 

References

BirdLife International. 2018. Species factsheet: Bubo shelleyi. Downloaded from http://www.birdlife.org on 02/02/2018.

Borrow, N.; Demey, R. 2001. Birds of western Africa. Christopher Helm, London.

Borrow, N.; Demey, R. 2010. Birds of Ghana. Christopher Helm, London.

Dowsett-Lemaire, F.; Dowsett, R. J. 2009. Comments on selected forest reserves in SW Ghana in 2009: wildlife and conservation status.

Dowsett-Lemaire, F.; Dowsett, R. J. 2014. The Birds of Ghana: an atlas and handbook. Tauraco Press, Liège, Belgium.

Grimes, L. G. 1987. The birds of Ghana. British Ornithologists’ Union, London.

Holt, D. W.; Berkley, R.; Deppe, C.; Enríquez Rocha, P.; Petersen, J. L.; Rangel Salazar, J. L.; Segars, K. P.; Wood, K. L.; Marks, J. S. 2018. Shelley’s Eagle-owl (Bubo shelleyi). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55018 on 2 February 2018).

König, C.; Weick, F. 2008. Owls of the World. 2nd edition. Christopher Helm, London.

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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2 Responses to Shelley’s Eagle-owl (Bubo shelleyi): revise global status?

  1. Hugo Rainey says:

    Very little is known about this species, but given the paucity of observations or other information the following statements can be inferred or are at least likely:
    1. It lives at low density and requires large areas of good quality forest habitat.
    2. It requires at least a reasonable density of prey populations (prey are poorly known but are at least >0.5kg).

    If these can be assumed, then this species may be at risk from the increasing fragmentation of the Central African forests and the past loss of forests in West Africa. Two recent papers indicate how loss of intact forests is ongoing and there are further unpublished data (C. Kiefer unpubl.) which indicate that very few sites in Central Africa are further than 20 km from roads. Loss and degradation of habitat is ongoing and unlikely to stop. Penetration of formerly remote areas by hunters along roads and loss of prey population from hunting is also ongoing. This loss of good quality habitat (ie large areas of good quality forest with reasonable prey populations) will therefore be much greater and be occurring more rapidly than the decline in forest cover alone.

    The reduction in habitat quality and loss of prey base suggest that this species is likely to decline in future and therefore already exceed the thresholds for Criteria A and C.
    Jones et al. 2018. http://science.sciencemag.org/content/360/6390/788
    Watson et al. 2018. https://www.nature.com/articles/s41559-018-0490-x

  2. James Westrip (BirdLife) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2018 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 2018 Red List categories will be published on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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