Sunday, 8 December 2013

Those pesky white-wingers!

No! I haven't just got back from dipping the Ivory Gulls...I don't have that kind of money or time right now!
In fact, I have been continuing my research on the Iceland/Kumlien's Gull complex. I have been giving a lot of Iceland Gulls the 'Hampton Scale' treatment and almost all the 1st winters I've come across pass as Kumlien's, particularly on the scale that correlates with Newfoundland gullers, I have to question the validity of the scale.
While I think the bird in my last post was certainly very dark, the primaries were very monotonal with no paler window in the inner primaries (kind of like what is seen in Herring Gull). From what I can tell, the birds that get accepted show an obvious darker wash to the outer 5 primaries compared to the inner 5. The same can't be said for 'my' bird. In addition, the bill was very bi-coloured, which again isn't a great feature for Kumlien's, particularly on the darker birds.

What you do have to then consider is what actually a Kumlien's Gull is. Is it a subspecies of Iceland or indeed Thayer's? Is it a hybrid between Thayer's and Kumlien's (which would certainly explain the variability)? Or, like a ring species, Iceland/Kumlien's/Thayer's are the same species that vary in plumage clinally over their geographic range and Thayer's are just at the darker end of the scale.

Anyway, whilst doing my research, I thought I'd bring back my 'confirmed' 2nd winter Kumlien's Gull from Nimmo's Pier.

Annoyingly, it appears that 2nd winter's are probably the most difficult age to have accepted as dark Iceland Gulls can look pretty dark.
Now, you can't argue that my bird has dark tips to the outer primaries, that's a given. However, the tail bar isn't very strong, despite being present. One thing that makes me think it could well be a Kumlien's Gull is that the gonydeal angle on the bill is rather pronounced and from underneath, it has a very Herring-like appearance. This could be a feature in its favour as it would appear that Thayer's and Kumlien's do look more substantial in appearance and have a more Herring-like head, so look less cute than an Iceland.
A feature I would like to bring up is the underwing of my bird. The wash to the primaries is very dirty, rather than the brilliant white seen on even the darkest 2nd winter Iceland Gulls. This seems to also be rather white in Kumlien's Gull, except a slightly darker wash on the darker birds. Therefore, as mine is on the paler end of the spectrum, I'm not quite sure what is causing the dirty wash.

Dark Iceland Gull

Dark Iceland Gull (all of the above) - M. Martens
(same bird in all pics) Quite a brutish looking Iceland and certainly on the much darker end of the spectrum. This bird has more extensive dark in the wings and a much darker tail than my bird. It does have a very white wash to the underwing primaries though. I am shocked at how dark this is though. If I found it, I regret to say that I would find it very hard to not call it a Kumlien's!

Pale Kumlien's Gull
overall pale Kumlien's Gull - Bruce Mactavish
This is quite a pale Kumlien's Gull. Much paler than the above Iceland. It has a nice greyish wash to the tail band, but although the overall pale tone is evident, it is certainly very desnely dark, rather than spotted. The out primaries have a dark wash, but unlike my bird, the dark extends right to the primary coverts, so the paler inner primaries really stand out.
pale-winged Kumlien's Gull - Silas Olofson
This bird has quite a similar primary patern to my bird, being at the paler end of the spectrum. The secondaries and darker basal colour to the tail stand out from Iceland though, so even this is paler winged than the Iceland Gull and my bird, this is 'just' a pale Kumlien's.
Dark Kumlien's - Dave Brown
Now this is at the darker end of the scale and the powerful angular head makes this look more Herring than Kumlien's. This shows a reasonably similar dark wash to the primaries on the underwing to my bird.

While I admit I am no expert on the Iceland/Kumlien's Gull complex, I am puzzled by this bird. At the time, I was pretty confident it was a Kumlien's and it certainly shows some features that are very good for one (e.g. head/bill, dark tips to the outer primaries, dark secondaries and dark underwings). On the other hand, the pale tail, limited darkness to the primaries point to Iceland. I am starting to think this is 'just' a dark Iceland.

Comments welcome

P.s. Sorry to the photographers on Gull Research for 'borrowing' their photos without permission!

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