Yellow-legged Gull

Yellow-legged Gull, Cottenham Long Drove, 4th October 2008, © Dick Newell
This bird is about as streaky-headed as nominate michahellis gets, it is also quite dark, although not quite as dark as it seems in this photograph. It is not fully adult, as evidenced by the black alula, so the lack of a mirror on P10 is not informative. However, one is tempted to speculate that it might be atlantis.