En underlig måge, men kan man udelukke at det er en artsren Sølvmåge med ringnæbbet-tendenser? Den mørkegrå rygfarve antyder ikke hybrid med ringnæbbet, men passer - hvis hybrid accepteres - bedre på at en Stormmåge kunne være impliceret.
Der er en kedelig tendens til, at alle fugle kan ikke umiddelbart kan bestemme, kategoriseres som hybrider. Måske skal forklaringen søges i den individuelle artsvariation.

A strange gull, but could an atypical small Herring Gull be excluded? The dark grey upperparts is not in line with the much paler of Ring-billed. If a hybrid is accepted, influence from Common Gull seems a better explanation.
Nowadays, the "hybrid ghost" is spreading, probably too much. First explanation should be sought after in the individual variation within a certain species.

I agree with Klaus that - if we are dealing with a hybrid -LBBG involment would seem a bit unlikely and that Common Gull might be a better explanation. A small Herring type doesn´t seem quite likely either given the features shown, such as greenish leggs and primary pattern. However, stranger things has happend! Here this gul appeard and as can be seen references are given by Brian to the spanish gull here which is rather similar and a few ears back (if by any chance the same individual), was suggested to be a possible California Gull here but this was soon rejected by the pale iris to mention one feature. On page 3 in this thread a second opinion was given by Daniel Velasco. Further suggestions of the spanish gull can be seen here

this link shows the spanish gull through the years.

JanJ