For those of you who don’t know, there is an ‘acro’ at Nanquidno that appears to be causing a few ID headaches. The views of many birders who have seen ‘it’ are varied. Some are saying its a Marsh, some Eastern Reed Warbler and others just a Eurasian Reed Warbler. There’s one thing for sure, unless it’s caught and feather samples taken for DNA analysis we’ll never know! Literature states that 1st year Marsh Warblers are difficult to seperate from Reed Warbler Acrocephalus scirpaceus. Svensson (1970) states that it is essential to obtain correct measurements and to get a co-worker to double check them! That obviously refers to birds in the hand, so birds in the field areÂ highly impossible to seperate on primary measurements alone. As far as plumage overall is concerned, Marsh Warbler has a warmer brown coloration and is often rufous-tinged on the rump and generally resembles A.Scirpaceus, though generally are slightly paler and more olive tinged above. In reality and in practice many appear identical. The tips to the inner six primaries are finely but clearly tipped whiteish, on average more obviously than in A.scirpaceus (but latter rarely just as pale-tipped).
The leg colour in Marsh Warbler is somewhat variable, though usually pinkish-straw in 1st year birds. The claw colour can be used as an ID aidÂ to birds in the hand. Â The feature is the contrast beteen the upper and underside of the claw. In A.scirpaceus there is a clear contrast between dark grey brown above and yellowish underside. This feature is almost impossible to distinguish in the field.
‘Eastern’ Reed Warbler Ssp.fuscus is slightly greyer olive brown than nominate, less tinged rufous above and slightly whiter, less creamy-buff on sides of breast and flanks.
The Nanquidno bird is very pale and was initially thought by some to be a ‘hippolais’ warbler due to its stance and bill size. The bill has a pale lower mandible. The primary projection appears long and the primaries show small buff tips. Legs are pinkish yellow but feet show pale in some photgraphs and darker in others. The bird is extremely skulking and rarely showed for more than a few seconds, so well done to the photgraphers who did manage record shots! If you do have any photographs and want to submit them for discussion, they would be very welcome. As mentioned earlier, unless the bird is caught it will probably remain as ‘Acro Sp’ on the reports.
P.Freestone and M.Halliday (c) Cornwall Birding 2008
Reference: Identification Guide to European Passerines Svensson (1970)
Photos: M.Halliday and S.Rogers