ID as per "Certainly More Than You Want to Know About the Fishes of the Pacific Coast," and this: http://www.fishbase.org/photos/PicturesSummary.php?ID=4192&what=species
I'm posting this because two birder dudes nearly got into a fistfight arguing whether this was "the" first cycle Little Gull of recent eBird fame, or a Bonaparte's Gull. :-O It was in a group of about 20 Bonaparte's. I have my opinion, but will leave it...
More prominent eye arcs than I've seen in Bonaparte's, but black bill unlike Franklin's. Unsure which one!
Flat body