Justification of Red List Category
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.
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).
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.
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).
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).
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).
Text account compilers
Butchart, S., Ekstrom, J., Harding, M., Martin, R
BirdLife International (2022) Species factsheet: Incana incana. Downloaded from http://www.birdlife.org on 01/12/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 01/12/2022.