11 November 2013

First winter Isabelline Shrikes – Alba Marsh (Bahrain)

Here are two ‘Isabelline Shrikes’ caught and ringed at Alba Marsh Bahrain last weekend, but which type or species are they? There are two types that occur in Saudi Arabia and Bahrain, The Daurian Shrike ‘isabellinus’ and the Turkestan Shrike ‘phoenicuroides’. These are treated as separate species by Panov 2009 and the latest IOC update v2.0, due to the spatial separation of breeding areas and the apparent absence of gene flow between them in allopatric/parapatric zones (Panov 2009).
Daurian Shrike is polytypic: in Panov's (2009) view, 3 sspp, isabellinus , (subsuming arenarius ) tsaidamensis, speculigerus . Winters much of South Central Asia, Southeast Iran and Afghanistan some reaching Turkey, Iraq, Kuwait, Saudi Arabia and other parts of the Arabian Peninsula as well as perhaps East Africa. Hybridises with Red-backed Shrike L collurio at range overlap.
Turkestan Shrike is monotypic Panov (2009). Winters Central Asia East & South of a line Aral-Southern Caspian including much Iran, Afghanistan,Kazakhstan, Tadzhikistan, Kyrgyzstan L&W 1997; Winters Southeast Iran, Southern Iraq, Kuwait, Saudi Arabia and other parts of the Arabian Peninsula & East & Weast Africa.

This species pair is difficult to identify in the field as first years unless classic birds are seen. These two birds are far from classic although it looks like both species may be involved. There is still a lot to learn about the true identification features of them and more careful study will hopefully help. DNA has been taken of these birds and will, hopefully allow us to identify them to species. Martin Garner recently put together a brief outline of the difference of the two species on his website:
First winter Daurian Shrike - Overall gingery wash to the brownish upperparts with gingery orange colouring prominent on the flanks but extending from rear flanks all the way up to below ear coverts. The centre of the throat and central breast/ belly are white. The tertials are darker brown but not strongly contrastng with the upper parts. Mask slightly darker brown with gingery wash at some angles- not blackish brown. Rump brighter orange with only very weak dark marks on some feathers tips. Orange centred median coverts
First winter Daurian Shrike - Should have cold earth brown to grey brown upper parts with darker (almost blackish) mask and flight feathers. Upper parts contrasting strongly with mostly clean white underparts marked with blacker bars/chevrons. More often retained juvenile feathers in rump and mantle/scapulars with white or black centres to median coverts (not orange).