So, here are my best (although still incredibly ropey) shots of the Co. Fermanagh Thayer's/Kumlien's Gull, taken on 6th January of this year at Lower Lough MacNean. They are unaltered, just cropped.
Although
thayeri was considered at the time, I came to the conclusion in the field that it was probably just a dark Kumlien's Gull (albeit a Thayer's lookalike). This was based on my views and interpretation of the bird's features (with the recent Dunbeg bird, to which I thought it showed many similarities, niggling at the back of my mind). A
combination of features that suggested identification away from a typical Thayer's Gull were:
- predominately pale scapulars (i.e. dark tips only)
- reasonably pale and well-marked tertials
- tail a milky dark brown rather than black
- primaries look a 'diluted' dark brown rather than black/near-black
- extensive pale in greater coverts as well as upperparts in general
- obvious pale base to bill
- relatively delicate structure
This bird was relocated, perhaps not unsurprisingly, some 10km or so to the east at Enniskillen Dump during late January, where much better views have since been obtained. And, judging from
Derek Charles' photos as well as this
youtube video, it looks an altogether more promising candidate. However, the features mentioned above still apply and, as such, it is far from a classic, dark juvenile Thayer's. Having said that, it does look "okay" for one.
Problem is, is looking "okay" good enough in a Western European context? In my opinion, probably not. While this bird may look alright on the west coast of the USA, in vagrant context (where Kumlien's Gull is a much more likely occurrence) the situation is somewhat different. I would have liked this bird to show a combination of darker primaries, secondaries and tertials, more extensively dark coverts and scapulars, and a more robust structure - many Thayer's just look bulkier than Iceland/Kumlien's, more akin to Herring Gulls (although don't get me wrong, this bird is within range; it looks bulkier than your average
glaucoides). Even if you take a holistic approach to studying this bird, I think it just seems to show a bit too much pale in it to confidently identify as an obvious
thayeri - particularly on the upperparts. That's not to say it isn't one, though.
To me, this is still one of the better candidates we've had in recent years - better than the
Dunbeg bird, the
Oxon/Derbys bird a few years back, and also the
Rossaveel 'thing' last winter. However, it doesn't quite look the dark juvenile Thayer's such as the
Ross Beach bird in early 2010 (wish I'd seen that one), and
Denmark in 2002. Obvious moult and wear aside, it doesn't actually look too dissimilar to the
2005 Barnatra bird.
So, to sum up... it's a dark member of the
glaucoides/
kumlieni/
thayeri complex. Great looking gull. Do I think this bird is a classic, unequivocal Thayer's Gull? No. Could it be one? Quite possibly, but also possibly not. We're such a long way from knowing the full extent of the problem that
kumlieni poses to the complex and as a result, it is surely not unreasonable to leave marginal birds such as this 'pending' until knowledge is enhanced.
One thing is for sure - if it isn't
thayeri, then my goodness can
kumlieni come close!