With a handful of lingering immatures mincing around throughout the spring and early summer, I guess it's fair to say that Yellow-legged Gulls have never actually left London. However, the annual mid-summer build-up of michahellis is now well underway and my first visit to the Thames for a couple of months revealed a handful of these entertaining birds. Curiously, none were juveniles - in fact most were 3cy.
Black-headed Gulls are also coming back in numbers - no Med yet though.
And, as always, it's worth keeping an eye out for rings. Here's a North Thames Gull Group bird that I'd not seen before.