10 December 2012

Pale Steppe Gull – Al Khobar Corniche

The Al Khobar Corniche site had a hundred plus Large White-headed Gulls (LWHG) of which one was a Caspian Gull Larus cachinnans type. Approximately 5% of the large white-headed gulls in the Eastern Province of Saudi Arabia are Caspian Gulls, which are an uncommon passage migrant and winter visitor. Numbers of Caspian Gulls in the Gulf region are relatively low although they may be overlooked due to their similarity to barabensis although another theory is that cachinnans is not such a strong migratory species and remains in the Caspian Sea area until it starts to get extremely cold and they are forced to move southwards. They then disperse to adjacent countries and only arrive in Saudi Arabia in mid-winter (October to November). The specific identification of taxa within the cline of the Steppe Gull-complex remains difficult, although in August the primary moult of Caspian Gull has replaced 5 – 7 primaries with P10 showing a negligible dark tip. Caspian Gull whose breeding range is the Black Sea, Caspian Sea and Aral Sea probably has a more westwards migration route to the Mediterranean where the majority of birds spend their winter. Some birds join Steppe Gulls Larus barabensis which travel through the breeding areas of cachinnans, on their migration south to the Gulf and spend the winter in the Arabian Peninsula.
Steppe Gull
After discussing this bird with Jan Jorgenson he mentioned it was probably a Steppe Gull Larus barabensis for the following reasons.
No visible pale tongue  on p10 (with a dark sub-terminal mark near the tip, which can be seen in some cachinnans as well), in the far wing, provided that it is p10, which I think it is due to relatively large mirror, which means that the primaries are fully grown. Fine streaking on the back of the head as well as structure. One can argue that the pale yellowish legs are more in line with cachinnans, since barabensis shows more vivid yellow legs - also at this time of year. Some variation is age related though. I would like to thank Jan Jorgenson, AbdulRahmen Al-sirhan and Yoav Perlman for very helpful discussion on the Large White-headed Gulls I have been seeing.