Doesn't look much at first glance does it? But that's because it's at the paler end of the sectrum.
I'm going to preach a bit now so most of you might want to click on one of the links to somebody else's blog. But as lots of people in Yorks don't know much about Gulls I'll bat on with a brief summary of the Kumlien's subject.
This is what most people think of as a Kumlien's Gull, lots of dark grey in the primaries but otherwise like an Iceland. The thing to understand is becuase it is widely believed to be or originate from a hybrid between Thayer's and Iceland any bird showing dark in the primaries, no matter how little has to be by definition a Kumlien's Gull. I remember Graham Catley photographing an adult bird in Lincs a few years ago which only had dark on the outer web of the outermost primary, the rest were classic Iceland Gull white. So if we accept that they are a hybrid and mega variable when adults then it stands to reason that juvs and imms will be just as variable.
I can't remember where I photographed this juv Iceland but note the lack of dark in the primaries. Actually this bird seems to show some dark on the second outermost primary, so it may not be the best example but I don't have any better ones and without a spread wing shot I can't tell if this is just shadow from the far wing folded over.
Compare the Barmston bird here and see how there is a dark shaded area either side of the shaft streak. On darker birds this will extend further toward the edges and show more dark with a thinner pale fringe.
Kumlien's also often shows a less rounded head shape but this is difficult to portray in pics as it changes so much with posture, overall though the bird appears less gentle and pigeon headed than the average Iceland
In this pic with the wings raised the extent of the dark shading becomes apparent. This pattern continues through all the primaries and onto the secondaries giving a hint of a secondary bar. Although my pics don't show it the tail is also similarly dark with a definite hint of a tail band. The next few shots further show the extent of dark in the wings.
Martin Garner has written about this bird on his excellent Birding frontiers blog and several prominent Gullers have commented. Perhaps the most enlightening is from Peter Kristensen who turns the argument round by asking the question if this was submitted as a nominate glaucoides Iceland would it be acceptable, and the answer to that is surely a great big NO.
OK Gull talk over sorry!!!