Hi Roger, you have captured a good pose here, and against a lovely blue water BG. You can post up to 1920 px wide which would surely bring this Gull more detail.
Beautiful gull indeed. Nice whites on the head, and good details. The blues in the BG look very appealing. I also like the overlapping feet. Good head angle, but a great one would have been a couple degrees more towards us.
I like the pose and the clean background. I like the rock as well. The sun seems like it was too high in the sky on this one. You have strong shadows on the belly of the bird and the whites of the head look too hot to me and lacking detail. Also I would clone out the white wash that is in between the shadow of the birds legs.