Slaty-backed Gull?

Yep, that is a question mark. Today, Lee Kay Ponds showed why it is the new Utah gulling hot spot with at least 9 species of gull present, including an adult Western Gull (probably the same bird from last year), at least 3, and maybe 4 Lesser Black-backed Gulls, 2 Mew Gulls, 1 Glaucous-winged Gull, 1 Glaucous Gull, 4 Thayer's Gulls, 115 Herring Gulls, 750 Ring-billed Gulls, and ~2500 California Gulls.

However, the most interesting bird was a 3rd winter gull that I think is a Slaty-backed Gull. However, since I have never seen one, and haven't spent a great deal of time studying this species, I am unsure of a few field marks which were off. In any event I will try to get back out there the next couple days to look around some more.

possible Slaty-backed Gull at Lee Kay Ponds. December 29, 2007

If it isn't a Slaty-backed, then it is a Western Gull, so a good bird, none-the-less!