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Socotra Warbler Incana incana

Justification
Although this species may have a small range, it is not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be small, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Taxonomic source(s)
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

Synonym(s)
Cisticola incanus Sibley and Monroe (1990, 1993), Cisticola incanus incanus Sibley and Monroe (1990, 1993)

Distribution and population
This species is a single-island endemic restricted to Socotra, Yemen, where it is locally common and apparently extensively distributed throughout the island. In 1964 the species was found to inhabit plains at Ras Kharma and Kallansiya, and up to 1,400 m in the Hagghier (=Haghir) mountains (Forbes-Watson 1964). During a survey of eastern Socotra in 1993 (Porter and Martins 1996), 135 were recorded at 11 sites in eight days, principally below 150 m, although some were found up to 850 m on Jabal Jaaf (Kirwan et al. 1996).

Population justification
The total population has been estimated to be in excess of 5,000 individuals (del Hoyo et al. 2006). Estimates of population densities were 27.5 and 3.9 individuals per km2 in the coastal plain and foothills respectively (with no data from the highlands) (Davidson 1996).

Trend justification
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.

Ecology
The species is found from sea level to c.800 m, although it has been recorded up to 1,400 m (Kirwan et al. 1996). It occurs in all types of scrub, most commonly in structurally distinctive Croton socotranus dominated associations, characterised by dense clusters of woody stems 1-2 m high, such as on the scarps of the northern edge of the Hamadiroh (=Hamaderoh) Plateau in east Socotra. This, and structurally similar vegetation, occurs patchily as understorey in areas where climax vegetation persists, such as at lower elevations on the northern foothills of the Hagghier (=Haghir) range and at Wadi Ayhaft (Dymond 1996). A pair have been recorded with three young in early January, and nesting behaviour and females ready to lay (deduced from collected birds) were also noted (Ogilvie-Grant and Forbes 1903). A nest discovered in February was a dome-shaped structure made from grass and lichen, with a side entrance, situated one metre above the ground in a bush (Ogilvie-Grant and Forbes 1903, confirmed by Forbes-Watson 1964).

Threats
Given the habitat requirements of the species, it is likely to be threatened by habitat loss, degradation and fragmentation. A substantial proportion of climax vegetation on Socotra has been destroyed through intense grazing and by the cutting of wood for timber and fuel. However, traditional grazing regimes include regular patterns of seasonal elevational movements of stock, as well as a system of spatial rotation, which may favour the species. Increases in grazing density through improved water distribution may impact the species, as may the rapid development of tourist infrastructure in the coastal region (Van Damme and Bansfield 2011).

In the event of extensive habitat loss or modification in the species' range, appropriate interventions should be made (e.g. impact assessments, increased protection of key areas).

Related state of the world's birds case studies

References
Davidson, P. 1996. Habitats and bird communities in southern Yemen and Socotra. Sandgrouse 17: 102-129.

del Hoyo, J.; Elliott, A.; Christie, D. 2006. Handbook of the Birds of the World, vol. 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona, Spain.

Dymond, J. N. 1996. The Socotra Warbler Incana incana. Sandgrouse 17: 142-144.

Forbes-Watson, A. 1964. Report on the Smithsonian Institution ornithological expedition to Socotra.

Kirwan, G. M.; Martins, R. P.; Morton, K. M.; Showler, D. A. 1996. The status of birds in Socotra and Abd Al-Kuri and the records of the OSME survey in spring 1993. Sandgrouse 17: 83-101.

Ogilvie-Grant, W. R.; Forbes, H. O. 1903. Birds of Sokotra and 'Abd al-Kuri. In: Forbes, H.O. (ed.), The natural history of Sokotra and 'Abd al-Kuri, pp. 19-72. Porter, London.

Porter, R. F.; Martins, R. P. 1996. Southern Yemen and Socotra: the report of the OSME survey in spring 1993. Sandgrouse 17: 1-188.

Van Damme, K. and Bansfield, L. 2011. Past and present human impcats on the biodiversity of Socotra Island (Yemen): implications for future conservation. Biodiversity Conservation in the Arabian Penninsula, Zoology in the Middle East Supplementum 3: 31-88.

Text account compilers
Butchart, S., Ekstrom, J., Harding, M., Martin, R

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Incana incana. Downloaded from http://www.birdlife.org on 12/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 12/07/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Key facts
Current IUCN Red List category Least Concern
Family Cisticolidae (Cisticolas and allies)
Species name author Sclater & Hartlaub, 1881
Population size mature individuals
Population trend Stable
Distribution size (breeding/resident) 3,600 km2
Country endemic? Yes
Links to further information
- Additional Information on this species