1 Dec 2014

North Caspian Taxon Eastern Stonechat S. m. hemprichii trapped and ringed in Bahrain – Alba Marsh

The latest data on the Stonechat Saxicola torquatus has found convincing reasons for recognising three species: European Stonechat S. rubicola, Eastern Stonechat S. Maurus and African Stonechat S. torqatus. The taxa breeding in the Caspian region, both of which winter in Saudi Arabia, were revisited and after studying the type description and various museum specimens it was concluded that the name variegatus should not be applied to the taxon breeding north of the Caucasus but rather to the population in eastern Turkey and Transcaucasia presently named armenicus. This means the former variegatus, northern Caspian population, needed a new name with hemprichii being the oldest available and valid name for the population. The paper also called hemprichii (formerly variegatus) North Caspian Taxon (NCT) and variegatus (formerly armenicus) South Caspian Taxon (SCT). The northern population NCT has a very characteristic male plumage with white portions on each side of the outer tail extending to half to three-quarters of the tail feather length, similar to many Wheatears and Red-backed Shrike. This can be seen easily when perched birds spread their tail or when birds fly but on perched birds with tails closed it can often not be seen. NCT also has a large unstreaked pale rump patch, buffish when fresh becoming white when abraded. In comparison European Stonechat has a streaked rump with usually limited white. Females are more difficult as they resemble both SCT and nominate birds and often need the tail coverts to be lifted to see the white (even in the hand), with a few females lacking any white at all. The South Caspian Taxon is similar to NCT birds but is larger, although a number of measurements overlap, has less white on the tail bases in male plumage (normally one-third to half the tail feathers white) often not visible in flight. Females invariably lack white in the tail. We caught a first year male NCT Eastern Stonechat S. m. hemprichii at Alba Marsh 28 November 2014 and studied the bird in the hand. It was sexed as a male due to the dark axillaries and dark feathers on the throat when these feathers were moved to expose the colour below. This is only the second Stonechat we have caught with the first not assigned properly due to the fact I did not lift the tail coverts to expose any white on the base of the tail feathers that it appeared to lack. I would like to thank Yoav Perlman for informing me of the need to lift the tail coverts to see the white on some birds in the hand, allowing me to do this on this bird and any subsequent ones we catch. Eastern Stonechat Saxicola maurus is an uncommon passage migrant and winter visitor with NCT Saxicola maurus hemprichii and STC Saxicola maurus variegatus occurring but NCT birds being the commoner type. Migrants occur mainly from March to April and September to November with many birds spending the winter where they are often seen in open areas with scattered bushes and in reeds beds near wetland areas as well as open fields.






No comments:

Post a Comment