Anjouan Scops-owl (Otus capnodes – BirdLife species factsheet) is currently classified as Critically Endangered because it has been considered to have a small population which is likely to be declining owing to continuing habitat destruction and degradation in its small range.
O. capnodes was rediscovered on Anjouan in the Comoro Islands in June 1992 (Safford 1993), after an absence of records dating back to 1886. The species survives in remnants of native upland forest and appears to be dependent on large trees with cavities for nesting and roosting (Safford 1993). The area of suitable habitat was estimated in 1992 to be within the range of 10-20 km2 (Safford 1993). However, surveys carried out in 2010-2011 suggested that the species may also be frequent at lower densities, in degraded forest and plantations and at elevations as low as 300m (Green 2010; Lloyd 2010; Green et al. 2015), although densities decrease in degraded forest and agroforestry (Safford 2013). Recent niche suitability modelling has estimated an area of occupancy (AOO) of 63km2 (Green et al. 2015), within an Extent of Occurrence (EOO) of 350km2.
The population has been variously estimated at 100-200 pairs (Safford 1993) and at 50-100 pairs (C. Marsh in litt. 2007, 2009), but recent surveys and habitat modelling have produced much higher estimates. Distance analysis in 2010 predicted a population density of 0.53 owls per hectare (0.44-0.63, 95% CI), resulting in a population estimate of 4,950 individuals (Lloyd 2010). A point count survey and distance analysis carried out in 2010-2011 produced an estimate of approximately 3,450 individual owls in the dry season and 5,450 in the wet season (the difference between the seasons was attributed to the presence of juveniles and higher detection probability during the breeding season; Green et al. 2015), equating to approximately 2,300 – 3,630 mature individuals.
The population size of O. capnodes is suspected to be decreasing as a result of the continued high level of deforestation on Anjouan, but the rate of decline is not thought likely to be high enough to warrant listing as Critically Endangered under the A criterion (Green et al. 2015) and the species has been found to be less dependent on undisturbed forest than previously thought (Green 2010; Lloyd 2010; Green et al. 2015). Plans are in place for the establishment of a network of protected areas in the Comoros Islands, although these are unlikely to include areas of degraded forest and agroforestry zones that have been shown to support O. capnodes (Green et al. 2015). Other threats to the species include invasive alien species such as the plants Rubus rosifolius and Lantana camara, the black rat Rattus rattus, which is abundant in the forest of Anjouan and may predate nests, and Common Myna Acridotheres tristis, which may compete for nest holes (Safford 1993, 2013). Severe cyclones are a regular threat to remaining forest fragments (Safford 1993).
O. capnodes is currently listed as Critically Endangered based on earlier estimates of its area of occupancy and population size, but more recent information suggestions that this classification is not justified. The revised estimate of 2,300 – 3,630 mature individuals (Green et al. 2015), together with the inferred and projected continuing decline in the species and the single subpopulation, means the species meets the conditions for listing the species as Endangered under Criterion C2a(ii). Confirmation of the very small AOO using 2km x 2km squares (as per IUCN guidelines; IUCN Standards and Petitions Subcommittee 2016), along with its very small EOO mean that the species would also qualify as Endangered under criteria B1ab(i,ii,iii,v)+2ab(i,ii,iii,v).
Additional information and comments on this proposal are welcomed.
Green, K. (2010). Encouraging results from the first comprehensive survey of the Anjouan Scops-owl. BirdLife Africa Newsletter 13(2): 25.
Green, K. E., Daniel, B. M., Lloyd, S. P., Said, I., Houmadi, A., Salim, D. M, M’Madi, S., Doulton, H. & Young, R. P. (2015) Out of the darkness: the first comprehensive survey of the Critically Endangered Anjouan Scops Owl Otus capnodes. Bird Conservation International 25 (3): 322-334..
IUCN Standards and Petitions Subcommittee. 2016. Guidelines for Using the IUCN Red List Categories and Criteria. Version 12. Prepared by the Standards and Petitions Subcommittee. Downloadable from http://www.iucnredlist.org/documents/RedListGuidelines.pdf
Lloyd, S. P. (2010). Habitat suitability modelling for the Anjouan Scops Owl, a cryptic unstudied species. MSc, Imperial College, London.
Safford, R. J. (1993). Rediscovery, taxonomy and conservation of the Anjouan Scops Owl Otus capnodes (Gurney 1889). Bird Conservation International, 3(01), 57-74.
Safford, R. J. (2013). Anjouan Scops-owl Otus capnodes; pp 572-574 in Safford, R. J. and Hawkins, A. F. A. (eds) The Birds of Africa. Volume VIII: The Malagasy Region. Christopher Helm, London.