? Seagull

A supersized seagull? Perhaps pregnant? ,or the alpha bird (if birds hand alphas) - Would be forced to go on a Gluten free diet if it moved to California as birds here watch their weight ---good eye - T

Juvenile herring gull by the look of it - yes they are considerably bigger than black headed gulls and are real bully boy scavengers

SorryEgret. I suspect its actually a Lesser Black-backed gull (or even a Yellow-legged gull). Note the 3 white bars in front of the tail where the juvenile Herring gull normaly shows spots. Actually I thought the head a bit pale for a herring gull, so consulted Collins bird guide.
Bird nerd!

Acomplished birdwatcher as I am I have never mastered the different 1st-3rd year summer and winter plumage (simplified) of gulls in their transition to adulthood.It's a whole subject in itself. Instead of there being, say, ten different gulls to learn you effectively have to learn about 30 at least!

The descriptions I've seen since posting suggest either the Great or Lesser Black-backed Gulls, the description of both juveniles seem very similar, whatever it is I was impressed by its plumage.

Many thanks to you all

True, they can be difficult. And I now think I got it wrong. Egret is probably correct!
Maurice