From Birds of Saudi Arabia blog; with more photos there:
21 May 2012
Whilst ringing at Alba Marsh last Friday Brendan and I caught five Reed Warblers. These are the first Reed Warblers we have caught for two months and were interesting as they are fuscus race Caspian Reed Warblers.
Eurasian Reed-Warbler Acrocephalus scirpaceus fuscus is sometimes treated as a separate species Caspian Reed-Warbler Acrocephalus (s) fuscus based on a paper by B. Leisler, P. Heidrich, K. Schulze-Hagen & M. Wink, Taxonomy and phylogeny of reed warblers (genus Acrocephalus) based on mtDNA sequences and morphology, Journal für Ornithologie 138 (1997): 469-496.
Caspian Reed Warbler breeds from the northern Caspian Sea to north-east Kazakhstan and east Iran; Asia Minor; Cyprus; Levant. They winter in Africa south of the Sahara.
European Reed Warbler breeds from North-west Africa & Europe east to central European Russia, Crimea & West Asia Minor. Winters in Africa south of the Sahara.
Some of the fetaures for Caspian Reed Warbler include white tips to the outer three or four tail feathers usually more obvious than Marsh or Reed Warbler. Pale grey-brown upper-parts, crown greyish, rump sandy coloured and slightly warmer toned than rest of upper-parts. Pale under-parts with only flanks brownish. Less rufous than European Reed Warbler.
Update: see here.
What Should You Do When Birds Collide With A Window? Here.