AN INTRIGUING ICELAND GULL

by Ian McKerchar

(Photo by Gavin Chambers)

During late July 2009 at Corsewall in Dumfries and Galloway, the gull in the photograph above had caused some debate amongst birders as to it's true identity. I was sent the above picture (and only this picture at that point) and asked my opinion as to whether the bird was an Iceland or Glaucous Gull. Both Iceland and Glaucous Gulls are uncommon in the UK during this time of year so this state of plumage is rarely documented but going off the features I could see and my 'gut feeling' I felt the bird was an Iceland Gull. 

Judging birds from a single photograph is often fraught with danger but with such a photograph it seemed reasonably straightforward. Ageing would always be the first port of call so this birds combination of very worn, faded and bleached plumage with some apparent first generation juvenile and typically pale biscuit coloured (think rich tea or a pale hob-nob) median coverts and scapulars with the bi-coloured bill and pale eye confirm that this bird is a second calendar year bird, moulting from first summer to second winter plumage.

It seems that the original confusion occurred from a couple of points. One that the bill was so bi-coloured, usually something we associate more with Glaucous Gulls of this age and that the bird apparently displayed an often rather un-characteristic head shape for an Iceland Gull. In fact it is not unusual for Iceland Gulls to attain such a bill pattern as our Corsewall bird but either way, for me it lacks the characteristic depth and heavy feel I associate with Glaucous Gulls. The head shape of this bird seemed to be highly variable, of course this is not unusual dependant on the bird's expression at the time etc but may have been accentuated by the heavily worn state of the birds plumage? Note at this point also the size of the bird's eye. Typically (for an Iceland Gull) large compared to the head as a whole and unlike the smaller eye we'd expect from a Glaucous Gull. Also, although the eye was undoubtedly pale, the strong sunlight here (and in other images taken in a similar light) seems to be over-emphasizing just how pale it was. There are much subtler structural or 'jizz' features which assist the pro-Iceland route although as always, using such features should only be in a supporting role rather than a confirmatory one. This gull appears relatively slender in body structure, even for a small female Glaucous and the closed wing lacks the bulk and 'depth' in the closed coverts of the broader winged Glaucous Gull.

Above: When I received this image (a few days after the initial header image), alarm bells rang, however briefly that might have been! It looks particularly 'snouty', the bill looks longer, the head smaller (despite Icelands generally having a smaller headed look in flight this looks oddly small) and the whole effect rings more of Herring Gull. Could it have been a leucistic Herring Gull? It still seemed highly unlikely but in the interest of thoroughness and to quash any doubts I contacted the photographers, Gavin Chambers and Chris Baines who kindly furnished me with the full suite of images containing the bird, many of which are reproduced below. (Photo by Gavin Chambers)

Above and immediately below: These images leaves little doubt that the bird was indeed an Iceland Gull and demonstrates just how variable that head shape could be. Here it is clearly rounded and full, the bill looks entirely more in proportion and the overall look is the 'gentle' expression we associate with classic Icelands. It's overall size is similar to the argenteus Herring Gulls around it, another pro-Iceland feature. Compare bill depths in the image below and note how the eye looks darker over the greater viewing distance involved in the image. (Photos by Gavin Chambers)

Above: Once again it's size can be accurately assessed in comparison to the other gulls around it but note the change in head shape that the bird's current expression creates. (Photos by Chris Baines)

Above: Another great shot of the bird relaxing in it's chosen pig pen! The outer primaries are so worn that assessing their apparent length beyond the tail tip becomes difficult, although in certain images it still appear perhaps too long for Glaucous Gull. Here the eye is in shade and the true colouration of the iris evident. (Photo by Gavin Chambers)

Above: Note just how worn the primaries are on this individual. Primaries p1-p3 are newly grown second generation feathers and p4 is in active growth. The remaining outer primaries are first generation, around a year old and are now showing their age and wear with it! (Photo by Chris Baines)

Check these interesting links below in connection with this Corsewall bird:

1/. http://www.cornwall-birding.co.uk/identification-articles/gull-id/ - This bird on the Hayle Estuary in Cornwall during early August 2009 is also, in my opinion, an Iceland Gull. It bears an almost identical state of wear and of median covert/scapular patternation as the Corsewall bird. The bill appears slightly shorter and deeper though.

2/. http://www.birdsireland.com/pages/rare_bird_news/2009/june_photos.html - This individual on the Kinnegar Shore, Belfast, Northern Ireland in late June 2009 bears such a strong resemblance to the Corsewall bird that one could be inclined to think it was the same bird! It's state of primary moult and wear matches the Scottish pig field loving bird and it has the same rather long-billed and snouty look about it but the black tip to it's bill appears more sharply demarcated with little if any bleeding into the pinker basal section.

3/. http://www.freewebs.com/richbonser/2008photographs.htm - Scroll down this page in Richard's website to find the Iceland Gull at Liscannor, County Clare, Ireland in August 2008. Once again it's state of plumage is almost identical to the Corsewall bird.

Acknowledgements

Thanks to Pete Berry for involving me in the discussion of this bird in the first place and to Rob Adderley and Rudy Offereins for useful discussion and input. Sincere thanks for the generosity of the two photographers Gavin Chambers (http://www.gavinsphotography.homecall.co.uk/) and Chris Baines, who not only allowed me to use their photos in this article but were kind enough to furnish me with their complete sets of excellent images.

Ian McKerchar, October 2009

Below: Iceland Gull, Corsewall, July 2009 (Photo by Chris Baines)

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