I have been persuaded that yesterday's Herring Gull, which appears to have the perfect wing tip pattern for Larus argentatus argentatus, is indeed our regular L. a. argenteus:
|the same wing inverted|
Brett S, whose expertise I respect in this matter, has advised me why via a comment on the new Dorset Bird News blog.
I agree entirely with the points he makes and was unaware that argenteus ever shows this amount of white on p9 (the second one from the end of the wing)! The lesson I draw from this is that, as he suggests, it's essential to take a holistic approach to identifying gulls, and not base the identification solely on a wing tip pattern alone. I'm now off to scrutinise even more of our own Herrings Gulls. This one appeared distinctly 'different' as it flew in from quite a distance. How long will it take me to find another argenteus with similarly white p9s?!
Thanks Brett, and good birding.