Friday, 25 January 2013

First for Yorkshire?

I can remember a few claims of Kumlien's Gull in the county over the last 10-15 yers but as I recall none of them have turned out to be gen.  The bird at Barmston therefore could well be the first documented record. That is of course that there aren't any pics of birds from way back when.

 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!!!


Anonymous said...

By these criteria, as opposed to the ones in Birding World 2000, the Whitby bird was Kumliens

Yorkslister said...

The Whitby bird wasn't a Kumlien's by these criteria. I haven't dug the Birding World article out but crucially that bird had complex internal markings in the primaries not an even wash. Maybe I wasn't very clear in the blog post and should have mentioned the Whitby bird but forgot! By the way why post anonymously, please leave a name in future

Anonymous said...

Not sure that 'hybrid' is the right word to use when talking about Kumlien's. It's not really comparable to, for example, Herring X LBBG or Glaucous X Herring where the parents are both clearly defined and the hybrids are fairly predictable in appearance. My understanding is that many Canadian researchers now regard Thayer's and Iceland to be at the ends of a dark to light west-east cline, with so-called "Kumlien's" being the result of gene flow between these extreme forms. This explains why Kumlien's is so variable.


Andrew Duff

Yorkslister said...

Thanks for your comments Andrew. I'm not too sure I agree with that as Thayer's and Iceland were once well separated and it's only relatively recently that the ranges have expanded and now meet. Having said that I'm sure we are still near the bottom of a steep learning curve and everything I/we believe now may prove to be incorrect in the future, but you have to start somewhere so calling this bird a hybrid is surely preferable to calling it an Iceland as some seem to be