African Scops-owl (Otus senegalensis) is being split: list O. feae as Endangered and O. socotranus 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.

African Scops-owl Otus senegalensis is being split into O. senegalensis, O. pamelae, O. socotranus and O. feae, following the application of criteria set out by Tobias et al. (2010) and consideration of recent evidence (Pons et al. 2013).

Prior to this taxonomic change, O. senegalensis (BirdLife species factsheet) was listed as being of Least Concern, on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.

O. feae is endemic to Annobón Island (Pagalu), Equatorial Guinea (König and Weick 2008). It was reported to be abundant in dense forest at 400-500 m by Fea in 1902, but may not have been recorded since the mid-20th century (Harrison 1990, Jones and Tye 2006).

Forest on Annobón is threatened by clearance for agriculture and development, including plantations of bananas, jackfruit, oil-palm  and mango (Harrison 1990, Jones and Tye 2006). However, changes to natural habitats have been reported to be much less extensive than on São Tomé and Príncipe (Harrison 1990), perhaps influenced by the relatively stable human population (Jones and Tye 2006). Former plantations of cocoa and coffee on Annobón have been abandoned, and are being colonised by kapok Ceiba pentandra, oil-palm, mango and tamarind (Jones and Tye 2006).

The species’s tolerance of habitat degradation and introduced tree species is not known, but it is precautionarily assumed to rely on undisturbed native forest, especially given that it has been described as rare in thick forest (Basilio 1957 in Harrison 1990). Following this reasoning, it is suggested that the species qualifies as Endangered or Critically Endangered under criterion C2a(ii), on the basis that its population numbers fewer than 2,500 mature individuals, and perhaps fewer than 250 mature individuals, and is inferred to be in on-going decline owing to habitat loss and alteration.

O. socotranus is endemic to Socotra Island, Yemen, where it is resident in semi-desert with scattered bushes and trees, generally in rocky landscapes (König and Weick 2008, Jennings 2010). It seems to prefer tree-lined wadis, especially with dense stands of palms; however, its habitat requirements have not been fully studied (Jennings 2010). It is characterised as generally not common, but locally numerous. Where suitable habitat is present, the species may occur close to human habitations. There is no information to suggest competition with other species for nesting sites (Jennings 2010).

Various surveys carried out between 1999 and 2007 indicate a population of c.300 pairs, although it could be more numerous (Jennings 2010). There is no historic information available to indicate any changes in its status or population (Jennings 2010). On the basis of this information, the species is assumed to have a population of fewer than 1,000 mature individuals, which is likely to be stable, therefore qualifying it as Vulnerable under criterion D.

O. senegalensis (as defined following the taxonomic change) is widespread in sub-Saharan Africa, where it occupies a variety of wooded habitats, whilst O. pamelae occurs in semi-desert in the Arabian Peninsula, in Saudi Arabia, Yemen, Oman and United Arab Emirates (König and Weick 2008). O. pamelae is locally common, and where it does occur it is probably the most abundant owl species (Jennings 2010).

Both O. senegalensis and O. pamelae are thought likely to qualify as being of Least Concern, on the basis that they do not approach the thresholds for Vulnerable under any of the IUCN Red List criteria.

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

References:

Harrison, M. J. S. (1990) A recent survey of the birds of Pagalu (Annobon). Malimbus 11: 135–143.

Jennings, M. C. (2010) Atlas of the breeding birds of Arabia. Fauna of Arabia 25. Frankfurt, Germany and Riyadh, Saudi Arabia: Senckenberg Gesellschaft für Naturforschung and King Abdulaziz City for Science and Technology.

Jones, P. and Tye, A. (2006) The birds of São Tome & Príncipe, with Annobón islands of the Gulf of Guinea: An annotated checklist. BOU Checklist No. 22. Oxford, UK: British Ornithologists’ Union and British Ornithologists’ Club.

König, C. and Weick, F. (2008) Owls of the world. Second edition. London: Christopher Helm.

Pons, J.-M., Kirwan, G., Porter, R. and Fuchs, J. (2013) A reappraisal of the systematic affinities of Socotran, Arabian and East African scops owls (Otus, Strigidae) using a combination of molecular, biometric and acoustic data. Ibis, doi: 10.1111/ibi.12041

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.

Related posts:

  1. Fea’s Petrel (Pterodroma feae) is being split: list P. deserta as Vulnerable and P. feae as Near Threatened?
  2. Archived 2010-2011 topics: Principe Thrush (Turdus xanthorhynchus): newly split and Critically Endangered?
  3. Houbara Bustard (Chlamydotis undulata) is being split: list C. macqueenii as Vulnerable and C. undulata as Least Concern?
  4. Madagascar Green-pigeon (Treron australis) is being split: list T. griveaudi as Endangered?
  5. Hottentot Buttonquail (Turnix hottentottus) is being split: list T. hottentottus as Endangered?
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4 Responses to African Scops-owl (Otus senegalensis) is being split: list O. feae as Endangered and O. socotranus as Vulnerable?

  1. Richard Porter says:

    I agree with both assessments.

    The following paper should be cited:
    Porter, RF & AS Suleiman. 2013. The populations and distribution of the breeding birds of the Socotra archipelago, Yemen: 1. Sandgrouse to Buntings. Sandgrouse 35: 43–81.

    For Socotra Scops Owl is reads (and the distribution is shown in a map):

    Socotra Scops Owl Otus socotranus (endemic, Figure 8, Plates 15, 16). This species is found in c45% of the area of Socotra and is the only breeding owl. Unsurprisingly none were encountered during transects but night time surveys showed it could be quite common in areas where there were good stands of mature trees, especially palms. They were recorded up to 850 m asl. Birds appeared to be most numerous in recording squares T5, U4, V5 and W5 where night surveys suggested a density of up to three birds singing/km2. Extrapolation is perhaps unwise but it would not be unreasonable to suggest each recording square where birds were present held over 50 pairs, indicating a Socotra population of c1000 pairs. Song was recorded 26 October3 April; two young in a nest on 19 February (estimated at c20 days old suggesting a laying date of 4/5 January) and recently fledged young (brood sizes of 1, 3 and 4) were found 16 Februarymid April. The taxonomic position and affinities of this owl are currently under investigation (Pons et al in prep).

  2. 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:

    O. senegalensis as Least Concern

    O. feae as Critically Endangered under criterion C2a(ii)

    O. socotranus as Least Concern

    O. pamelae 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.

    • Martim Melo says:

      Annobón Scops Owl
      We have recently sequenced a nuclear (intron Myo2) and a mitochondrial marker (ND2) from a sample of Otus [senegalensis] feae collected by Iñaki Rodríguez-Prieto in an expedition to Annobón in January 2009. Surprisingly, there is no differentiation from Otus senegalensis. The nuclear sequence was identical and only 7 base pairs differed for the ND2 (about 1% sequence divergence). This is well-within normal levels of intra-specific genetic variation: for example Otus hartlaubi, from the neighbouring island of São Tomé has more than 70 base pair differences in relation to Otus senegalensis.

      This lack of differentiation is indeed odd considering the level of isolation of Annobón and how distant are the closest Otus senegalensis populations (not present on the mainland at the same latitude as Annobón). This may reflect a very recent colonisation event with little time for genetic differentiation to show up – as there is little reason to believe there is any ongoing, regular, gene flow between Annobón and the mainland populations.

      The genetic results are important data relating to the taxonomic decision of treating the scops owl from Annobón as a distinct species. Considering that Otus species can exhibit a large range of intra-specific phenotypic variation (often structured into different ‘morphs’), the strongest argument for justifying the split of the Scops from Annobón appears now to be exclusively inferential: we deduce that the high level of isolation implies that the population will be evolving independently, even if it colonised the island only very recently. I admit that I am not sure if this statement is correct: has a proper morphometric comparison, taking into account the normal patterns of intra-specific variation in the group, and the study of its song been done with results giving further support for the split?

      In any case, the genetic data highlights the need to treat the ‘species status’ of the Annobón scops owl with the acknowledgment that this may be the most parsimonious option, but that ultimately the question remains unresolved. The split is also the most precautionary option: it will give support to protect this endangered population (and an very interesting one from an evolutionary perspective) as one tries to gather additional data on its evolutionary history. Otherwise, a more definitive answer may be reached when the Annobón owl is no longer present among us.

      We plan to sequence two additional genes and another individual (museum specimen) before publishing these results.

  3. 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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