German-ringed Yellow-legged Gull 'H8J0'
Close-up of the darvic; use your imagination!
Thankfully, the idea that this bird was Herring (or even Lesser Black-backed) turned out to be as far-fetched as it seemed in the field on Sunday - this bird was pulli ringed as a michahellis in a colony in central Frankfurt on May 18th. Relief all round, and no need to throw any of our present understanding (and literature) in the bin! Here's the beef:
Thanks to Rich for getting on with the detective work; unfortunately my blog looks a bit of a clone of his at present, although he is off on holiday for a few weeks and thus I might actually have something to post that he doesn't.