Thursday, 1 January 2009

Local birding: The 'Yellow-legged Gull' of 30th Dec revisited.

I thought I would post an update on this bird in light of opinions sought from two very experienced Gull enthusiasts, which may be helpful to anyone at my (moderate) level of experience and below.

Certainly with large Gulls, I personally try and strive to maintain a level of super-cautious self dicipline when it comes to claiming both Caspian AND Yellow-legged Gulls and my main aim with this bird was to see whether I could 'push' my own boundaries by seeing whether I could confidently clinch a Yellow-legged Gull locally in views such as this of birds on the water, and even if ALL features were not adequately documented.

For the majority of the time, c10 minutes at dawn, the distant bird sat motionless on the water, then washed & preened for the final couple of minutes, lifting up and down as it flapped whilst I filmed it, just before it flew off.

On reviewing the footage, I was never comfortable with the perceived pinkish leg colour in a bird of this age and after an evening of pouring over the images and literature, I arrived at the conclusion that everything fitted a YLG of this apparent age except the leg colour, which certainly showed pink at least mixed in. But did that mean that it was definately not a YLG as everything else in terms of plumage and structure appeared to fit very well?

Having let multiple birds similar to this this 'go' over the years, I concluded some time ago that in order to learn as much as possible from birds like this when I hit the 'brick-wall' of my own experience, the best thing to do was to email images to respected birders with infinately more experience in this field for their comments. These are reproduced below the images.

Dick Newell: I think you are right Bill, it looks fairly typical of Yellow-legged Gulls around here (Peterborough area) at the moment.

Alan Dean: Your photos have very much the ‘character’ of a YLG but, personally, I wouldn’t want to make a categorical identification from photos taken in such unhelpful light conditions.
What can be seen of the wing-pattern seems to fit, as does the apparent shade of the mantle – though again ‘low’ light conditions can make an accurate appraisal difficult.
It is always worth ‘checking out’ any large gull with a clean white head in winter but, after about mid-December, it does not mean too much in itself, as from around that time Herring Gulls can acquire a very white head. They then look very different from nearby birds – especially Scandinavian birds – with very streaky and messy looking heads.
I’m sure that here in my own area some people erroneously identify HGs as YLGs at this time of the year because they are over-reliant on a white head as an id feature.
In your photos the legs do look rather pink. This may be a photographic artefact (yellow can sometimes become very suppressed in photos) while some YLGs can have rather colourless greyish-flesh legs – especially sub-adults. I have recently been discussing with Dick such a bird, which I saw here in the midlands. However, I seem to detect suggestions of quite intense pink in one or two of your photos and, if this were genuine, it would be unlikely in YLG, certainly in an adult bird.
Thus, on the basis of apparent mantle colour in combination with apparent wing-pattern, I strongly suspect that your bird is a YLG but I would require more ‘unequivocal photos’ of these and other features before proffering a confident diagnosis.
Many thanks to Dick & Alan for their comments.

So, in keeping with my regime of trying to be as cautious as possible, i'm content to downgrade this to an inconclusive YLG solely on the apparent anomalous leg colour coupled with the apparent age of the bird.

Postscript: Browsing through my limited archive of local YLG images, this bird, considered a good YLG at the time, perhaps shows a leg colour reminiscent of my impression of the 30th Dec bird: