JULY 2010'S MYSTERY BIRD ANSWERS
A satisfying 22 entries this month was once again much higher than I had anticipated with only a week left to go in the month (and very few answers received!) and, once again, restored my faith that it is worth carrying on and at least some birders are getting something positive out of it besides just good fun. A big thanks to everyone who made the effort once again but it's something of a shame that throughout the year there have been a total of 42 entrants so far. Where are they all now?
Mystery Bird 13
I am pure evil and I know it! This was, in my humble opinion, the most difficult mystery bird of perhaps the entire competition to date. Why you may ask? After all, it is clearly not the usual 'arse end' view nor something cryptic that really 'twists your melon man'! Rather, it is a full image of the bird, there for all to see, so why the difficulty? Two reasons:
- The lighting of the image. Just how much effect is it having on our assessment of colour hues?
- Most importantly, especially bearing in mind point one above, it is an acrocephalus warbler as everyone thankfully guessed and that means it could be an absolute nightmare to identify!
Now don't get me wrong, they're not all or indeed always that difficult and despite my own experience of seeing and carefully studying good numbers of all the Western Palearctic species occurring in Britain, mistakes still happen. In fact, the reason I know what species this mystery bird actually is was learned from such a mistake I made! My dad always said I'd go through life learning by my mistakes (mainly as I wouldn't listen to anyone else's advice) and by and large he's always been right. Cheers dad!
Okay, so onto the bird. It's an acrocephalus warbler and everyone managed that, which is great as such immediate identifications are usually borne out of a 'feel' for the species and getting that far atleast narrows our choices down. It's unstreaked and rather uniform, almost featureless appearance leaves us with three main choices which the 22 entries also narrowed it down to, other than one who remained undecided and claimed a point for warbler instead. And why not ☺! The choices were for Blyth's Reed Warbler, Marsh Warbler and Reed Warbler. Yet again, the explanations provided by some entrants was equally very enlightening and commendable but at the same time their perception of certain features varied considerably between them and highlighted the necessary caution in their use. To be fair, it seems that the strong sunlight has burned out pretty much all the colour from the bird although one observer felt that the uppertail coverts we can see, looked quite reddish-brown. This individual is also an adult (collecting food for it's young no doubt) and is typically very worn (check out those ragged tertials) which can also have an effect to dull the plumage slightly. Entrants found two main features with which to decide their answers on and they were the strength of the supercilium and eyering plus the apparent length of the exposed primaries beyond the tertials. The first feature is unfortunately pretty much useless in assisting our decision I'm afraid. The strength of the supercilium and/or eyering is subject to considerable overlap within the three suggested species, is dependant to some extent on viewing angle and lighting and as such cannot really help us. The length of the primaries however does vary between the three species. Marsh has the longest (68-76mm according to Svensson), Reed comes next (62-73mm according to Svensson) and Blyth's Reed has the shortest (58-65mm according to Svensson). So what does this tell us? That judging the length of the exposed primaries is often more difficult that we might at first appreciate! To this end, some entrants felt they were short on our mystery bird, short enough to be a Blyth's Reed. Others were certain they were so long that they could only belong to a Marsh Warbler and some felt they fell in between (or just couldn't decide either way!) and plumped for Reed. To confuse you further, take a look at the apparent primary lengths of the species below, all courtesy of the North Ronaldsay Bird Observatory (cheers Paul):
Above: Blyth's Reed Warbler. Rather short, rounded primaries? But still two thirds the length of the tertials?
Above: Marsh Warbler. Certainly long, as long as the tertials?
Above: Reed Warbler. Hmmm, long primaries, also as long as the tertials?
The exposed primaries beyond the tertials of our mystery bird appear to my eyes to fall roughly about three quarters of the length of the tertials themselves and are therefore perhaps too long for Blyth's Reed. The latter species also tends towards a more rounded looking wing (clearly appreciable in the photo above) due to the outer primaries being of a more similar length and our mystery bird doesn't have this 'feel' to it. Marsh and Reed Warbler, as said earlier, can be an absolute nightmare to separate and the colour rendition of our mystery bird image doesn't assist us in any way. How much we can reply on the alleged slightly more reddish-brown hue seen on the uppertail coverts I'm not sure given the image we are presented with. Jizz won't help us here either but the legs of our bird do indeed seem very pale, yellowish perhaps and that surely gives us a clue to favour Marsh Warbler? Perhaps, but there is one glaring identification feature to assist us to separate them. It is a feature which I learned the presence of the hard way but which since then has assisted me with the identification of several contentious individuals (anyone see the alleged Marsh Warbler at Frodsham a few years ago?) and is patently visible in the field provided it is studied carefully and good views are obtained. The feature lies, yet again (bearing in mind May 2010's mystery phylloscopus warbler) within the bird's wing. Marsh and Reed Warbler have different lengths of the emargination on the third primary, a feature which can clearly be seen on our mystery bird. Note where this primary (which is actually second from the outside edge of the wing) falls away from the outer primary (which like the others is straight edged) and this is the emargination. It can be seen to be emarginated quite high up the primary and roughly falls in-line with the tip of the longest tertial and therefore p10, which is the shortest primary. So, on our mystery bird, the emargination to p3 falls roughly in-line with p10. On Marsh Warbler the emargination to p3 is noticeably further down the wing, towards the wing tip and generally falls in-line with p7. Whilst it might not sound like much this is patently different from our mystery bird and the fact that Reed Warbler shares our mystery bird's p3 pattern leaves us with our correct answer. And so it was the case with my own mistake all those years ago, you live and you learn! As a side issue, both Reed and Marsh Warbler generally have only one emargination to the primaries, that on p3 whereas Blyth's Reed Warbler generally has atleast two, on p3 and p4 and infrequently can have one on p5, though that can all occasionally go out of the window and it can have a pattern very similar to Reed Warbler. Just thought I'd drop that pearl in to throw you off again!
Quite why the legs of this individual appear so pale I'm not sure, individual variation perhaps but it proves a point that there is obviously overlap there too and that basing an identification on one variable feature can lead you astray. The emargination to p3 can be seen even better on the image below and the upperparts look all the more brighter and reddish-brown as we would expect with the species. Either by careful consideration or just plain good fortune, 45% of all entrants managed to correctly identify this mystery bird so 'big up yourselves' Geoff Hargreaves, Michel Rogg, Nick Hilton. Neil Calbrade, John Tymon, Paul Brown, Gary Crowder, Simon Warford, Dave Broome and Iain Johnson. A special mention to both John Rayner and Gary Crowder who also managed to identify the mystery bird's prey item as an Emerald Damselfly, apparently!
Reed Warbler, Mere Sands, Lancashire, June 2010 (Dennis Atherton)
Mystery Bird 14
Hooray, it's not a warbler! Though it was of course yet another arse end! But whose arse end was it? A majority of 77% managed this one spot on, though three species were incorrectly offered as answers to it's identification. The first, Little Ringed Plover, does indeed have rather plain brown upperparts similar to our mystery bird and also has similarly coloured legs but unless it is holding a stick in it's bill to probe in the mud (!) it clearly doesn't match the long bill of our mystery bird. Marsh Sandpiper was also suggested but it's legs are never quite so blatantly orange-yellow coloured and the apparent bill 'weight' doesn't match either (amongst other things). The final incorrect species managed three votes, but Greater Yellowlegs, whilst having the correct bill 'weight' and leg colouration of our mystery bird has consistently and strongly notched edges to the upperparts. Our mystery bird is clearly uniformly brown on the upperparts, lacking any pale notching of any kind, so Greater Yellowlegs it is not. As the 77% worked out, only one species fits the bill (no pun intended ☺) and Terek Sandpiper it was!
Terek Sandpiper, Qatar, April 2010 (Ian McKerchar)
Nine entrants nailed both species this month in what was a real test of your resolve. Many potential entrants may have been put off by the apparent difficulty of the acro in particular but as the intrepid twenty two admirably displayed, it's not the winning, it is indeed the taking part which matters! Well done anyway to those who did the double, Geoff Hargreaves, Nick Hilton, Neil Calbrade (who tried his best to read the ring number in his assessment process!), John Tymon, Paul Brown, Gary Crowder, Simon Warford, Dave Broome and Iain Johnson.
The lead remains the same with Paul Brown ahead by a single point. However, the battle for second rages with John Tymon and Neil Calbrade both with only one point dropped this year. Keep at it everyone, it is appreciated and I'll continue the competition as long as you continue entering!
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