Time to reflect,
The 'Yellow legged gull' that was present on Nov 5th at Prescot reservoirs and was well photographed below, failed to muster any imput on its id so I will have to draw my own conclusions on this interesting gull. I now think that this gull was an Argentatus herring gull.
All the 4 features below can occur on michahellis and argentatus : The last three features usually attributed to michahellis.
red gonys spot reaching upper mandible
lightly streaked head in early winter
but the wing pattern of this gull can only be Argentatus.I have tried to find images of Michahellis without black on P5 and failed so this is the main reason for my decision.If I had not taken the photo of the open wing showing the primary pattern then I would have certainly recorded this bird as michahellis as I am sure most others would have.
Initially I thought eastern Mediterranean and Black sea populations would fit but these birds still show black on p5 although to a lesser degree.
So next time you see an adult winter 'Yellow legged gull' just take a closer look. I think if this bird would have been seen standing it would have made the id much easier but it was only ever seen on the water. Please feel free to agree or disagree with the above but for me this bird was an Argentatus.
I suppose now that I have made my mind up on what this bird was, it makes the bird even more interesting for me as I have never seen a yellow legged argentatus before. Anyway thats gulling for you, not everyones cup of tea I know but come the winter it certainly keeps me interested.