27 December 2013

Caspian Stonechat – Sabkhat Al Fasl

Whilst birding at Sabkhat Al Fasl I found a very nice male Caspian Stonechat. The Stonechat complex is as its name suggests is very complex and a new paper has been written by Lars Svensson, Hadoram Shirihai, Sylke Frahnert & Edward C. Dickinson on the Taxonomy and nomenclature of the Stonechat complex Saxicola torquatus sensu lato in the Caspian region. This paper suggests that the mainly Asian form becomes the Eastern Stonechat S. maurus (Pallas, 1773). This species has several recognised subspecies, with three occurring in Saudi Arabia as well as being Palearctic taxa: maurus breeding in Russia and marginally in adjacent parts of eastern Europe, in western and south-central Siberia, Kazakhstan and parts of Transcaspia, east to north-west Mongolia and south to Afghanistan and northern Pakistan (possibly also in north-east Iran); variegatus (S. G. Gmelin, 1774) in eastern Ukraine on the lower Don, east Crimea, the Kalmykiya plains north-east to the Volga Delta area, in the south on the northern slopes of Caucasus, apparently reaching north Azerbaijan (named as ‘NCT’ for ‘North Caspian Taxon’); and armenicus Stegmann, 1935, in north-east Turkey, Caucasus (apparently at least locally on the southern slopes), Transcaucasia and western and southern Iran (named as ‘SCT’ for ‘South Caspian Taxon’).

Birds previously known as Caspian Stonechat Saxicola torquatus variegatus are thus now known as North Caspian Taxon (NCT). The paper states that the northern population has a very characteristic male plumage with extensive white portions on each side of the inner tail (between half and three-quarters of the outer tail feathers white), not unlike the pattern in many wheatears or male Red-backed Shrike Lanius collurio. This can clearly be seen in the flight shots of the bird I found at Sabkhat Al Fasl with the paper saying it can easily be seen on a flying bird, but can be more difficult to confirm on perched birds with closed tails. The amount of white in the tail on males is subject to a subtle cline; at its maximum in the Volga Delta region, becoming slightly more restricted in the south. Both sexes resemble nominate maurus from further east and north in that they have a large unstreaked pale rump patch, buffish when fresh, white when abraded and bleached. In comparison, European Stonechat S. rubicola has a streaked rump with usually limited white. The NCT male has a concentrated red-brown chest patch and a large white patch on the neck-sides, again more like nominate maurus and different from most rubicola which again can be seen on the photogrpahs of the Sabkhat Al Fasl bird. The NCT female is very similar to females of nominate maurus and usually can be identified only if handled. The female has much less white on the base of the rectrices than the male, generally requiring that the tail-coverts be lifted to reveal the white, and a few females lack any. The name used for the NCT in Vaurie (1959), Ripley (1964), Urquhart (2002) and Dickinson (2003) has been variegatus.