(NH) Heres Dick Coombes reveal shot for last Fridays Headwrecker: a lovely Wood Warbler, one of Irelands scarcest and most restricted breeding birds. Small numbers do breed in the oak woodlands of Co. Wicklow (and occasionally other counties too) each year, but finding them is very difficult. Across the water in Wales they are much more numerous and not difficult to track down if you know their distinctive spinning coin song. We didnt have such a good view of the bird originally (reposted here for ease of reference), so how could you have worked it out? It was clearly a small passerine bird, very white below (at least on the flanks and lower belly) and distinctly greenish above. It also had long wings and very long undertail coverts, both of which features made it look very short-tailed (even though it really isnt). The greenish colouration, contrasting pale underparts, small size and short-tailed look, as well as the square or even slightly rounded end to the tail (which is obviously not forked or notched, like that of a finch, bunting or sparrow) allow us to narrow it down to being either a warbler or a kinglet (i.e., a Goldcrest or Firecrest). I know that the small size and stubby-looking tail might have suggested Wren, but that species would be much browner overall, without quite so much contrast between upper- and underparts and with distinct barring on the flanks. It looks better for a Goldcrest (or Firecrest), but the flanks are too brightly white for either of those, and even on the unhelpful angle we had the white wingbars of both of these species would have been visible: our birds wings are just too plain and uniform. No, its a warbler, and judging by the greenish upperparts its one of the ones that belongs to the genus Phylloscopus. The commonest of these in Ireland, by a long way, are the dreaded confusion pair of Chiffchaff and Willow Warbler (both long-standing Whoami favourites). We couldnt make out the colour of our birds legs, but from its very long primary projection (i.e., the distance that the its longest primary feather projects past the tip of the tertial feathers) we can at least be confident that it couldnt be a Chiffchaff. It also looks a bit too crisply white below to be a Chiffchaff anyway. Other, rarer, Phylloscs, such as Arctic, Raddes and Dusky Warbler, would also have much dirtier flanks, contrasting much less with the upperparts. A Greenish Warbler could look very like our bird, but again the primary projection is just too long, and we would be able to see a thin pale wingbar on the tips of the greater coverts if it was that species. Likewise, the more prominent wingbars on a Yellow-browed Warbler, Humes Leaf Warbler or Pallas Warbler would also be visible, so they can be ruled out too. So, that really just leaves us with a choice between Willow Warbler and Wood Warbler, both of which have plain wings and long primary projection. The fact that the primary projection is very long indeed suggests Wood Warbler, and the crisp white flank colour fits better for that species too. Beware, however, of relying too much on these features, given the odd angle of the photo (which makes the bird look even shorter than it is) and the fact that it is in strong sunlight. How can we be absolutely certain? Well, look at those undertail coverts, which are so long and extensive that they cover (which, after all, is what coverts do) most of the underside of the tail. A Willow Warbler would have much shorter undertail coverts, but they are perfect for a Wood Warbler, so we can be sure thats what it is: bonus points to Kevin Barry for twigging this. Well done if you got it right: it was a tricky one.
Posted on: Mon, 07 Jul 2014 13:59:50 +0000
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