Over the past few years I have seen three Blyth's Reed Warblers in Britain and the last one, on Fair Isle in 2011, was mist netted and ringed and so I was able to get some in-hand shots of the bird. The photos have been sitting on my hard drive serving very little purpose since then. I thought I'd stick a few on my blog so that they are available for anyone wanting help with identifying putative Blyth's Reed Warblers or who just want to brush up their ID skills.
Blyth's Reed is an un-streaked Acrocephalus and as such is pretty difficult to identify as there are a number of other, very similar, un-streaked Acrocephalus warblers in the Palearctic region. Blyth's, Marsh and Eurasian Reed can all be told apart on song but the chances are a bird in the UK will be a first-winter bird in the autumn and will be silent. If it does call you are listening for a Lesser Whitethroat type 'tuk' which is unlike the 'tcharrr' of a Eurasian Reed or the softer note of a Marsh warbler. So what do you look for in a Blyth's? They have a combination of relatively short primary projection and clear emargination on two of the primaries. O.K. if you have a bird in the hand but difficult in the field! The emargination on the primaries can be seen on the first photograph but it would not, I suggest, be of much use generally.
1st autumn Blyth's Reed Warbler Acrocephalus dumetorum Fair Isle October 2011 |
1st autumn Blyth's Reed Warbler Acrocephalus dumetorum Fair Isle October 2011 |
In this third picture we can see that the bill is quite deep and broad based and so it appears to be more substantial than on Eurasian Reed Warbler but they tend to be about the same length. The bill of Marsh Warbler is slightly smaller. Guidebooks always point to the long, sloping forehead and the low angular crown, peaking just after the eye as a useful ID feature of Blyth's and again this feature can clearly be seen in these photographs. This bird has a clear open-faced expression that can also be a useful ID feature of Blyth's.
There are a number of confusion species. As well as Marsh and Eurasian Reed, Large-billed Reed Warbler Acrocephalus orinus is probably the most difficult to tell apart - fortunately not a problem in Britain...not yet!
Back on Fair Isle during the week of September 18th to 25th I witnessed a repeat performance as another Blyth's Reed was located, captured and ringed. This bird then hung around showing well on and off in a couple of crofters' gardens for the rest of the week. I took photos of the bird in the hand. The next three photographs are of the 2015 bird.The gingery colouration on the primaries and secondaries is quite noticeable on this bird. Note the pale pink lower mandible. The wing length of this bird was 60.5 mm. I think that the wing length for Eurasian Reed Warbler lies between 65 and 70mm so the wing length of this bird is quite short in comparison. |