Hi Phil,
At the risk of being somewhat pedantic, might I point out that, as Reed Warbler is by far the commonest possibility, and as this would be on the early side for Marsh Warbler (but after the arrival of the bulk of the Reed Warbler population), then a sensible opening position is to assume that it's a Reed and try to disprove this hypothesis?
In trying to do so, I find it extremely hard to exclude Reed: while not foolproof, many of the features that I would instinctively look for in pics, such as the (approximate) position of the emargination on the third primary, are not visible, at least not with any certainty, and some features seem to look better for Marsh in some pics than in others. For example, the head pattern that looks so good in a few pics, with an apparently contrasting supraloral (almost on a par with a Blyth's Reed), looks distinctly less impressive at
http://www.brandonbirding.co.uk/marshwarbler/slides/MarshWarbler11.asp, with the eye-ring seeming to dominate the facial pattern more than the supercilium, a pro-Reed feature. The claws, as can be seen, seem longer than one would like for a 'classic' Marsh, but perhaps the apparent length is misleading: nevertheless, questions are raised. The bill could perhaps be a little long and thin for Marsh, but the angle does not allow this to be judged properly, the primary projection could fit either species, and, as a result, I find myself wondering if this may actually be a Reed, even if
proving this could prove tough...
Regards,
Harry
