At Allerton today, I visited early afternoon, and with the wind direction, sunlight and where the gulls were, good views were had of many of the gulls, although some were still fairly distant. The highlights today were two 1st-year Iceland Gulls, two advanced 2nd-year birds with olive/orangey yellow bills with no dark tips, also the 2nd-year Glaucous from yesterday.
I came across this 1st-winter bird with washed-out tertials and primaries, probably the same as that seen at Farnham, and had several minutes view at 150m range, although it was asleep for the most part. It briefly raised its head to reveal a small head, neat all dark bill with a hint of pale (red?) at base. Of c1000 Herring Gulls present, it was the only one showing any hint of such washed out primary-tips.
The options are that it is (a) an Argentatus Herring Gull from the pale end of variation, (b) a Kumlein's Gull from the darkest end of the spectrum, (c) a hybrid (although presumably not x Glaucous due small size and small dark bill), or (d) a leucistic bird. I am open to suggestions, and any thoughts or comments would be welcomed.