Hi Joe. My guess is that this is a Great Black-backed Gull, (2nd winter). This is based on the huge looking bill and the mostly black tip. It would help if you had a shot of the back/mantle of this bird! As for resources, Nat. Geographic Birds of N.A. 5th edition and the Sibley Guide to Birds are good. If you really want to go whole hog (gull!), you can use Gulls of the Americas, by Howell and Dunn or Gulls of N.A. Europe, and Asia by Olsen and Larsson. Good luck!
I will have to take a look at GBB gull. That actually does make sense as I don't recall seeing any mature Ring-Billed gulls around , but there was at least one mature GBB gull.
Joe- There is the Gulls of North America, Europe, and Asia by Klaus Malling Olsen & Hans Larsson and Gulls: Guide to Identification by the late P.J. Grant.
This one does have the head-look of a GBBG but the bills of young ones tend to be pinkish, not yellow (not until they get older at least). Did the bird have a black-back?
I wish I could remember what the back looked like , but there were quite a few gulls around and I can't quite recall. From the area of the upper back that is visible in the photo it appears that the upper back, at least, is white.
When I first looked at this my immediate thought was of a 2nd summer Herring Gull. Then when I looked at several field guides including the 2 "Gull books" mentioned in the thread I realized how similar GBB and Herring gulls in this plumage would be when the upper surface of the wings can't be seen, as in Joe's photo. Anyway, I enclose a recent image of a definite Herring Gull in this plumage, over a field close to home, and I think it shows all the similarities to the bird in question, allowing for the different lighting.
Richard, that does look like a match. The puzzling part is that there were at least one other GBBG in the flock I was shooting , and I don't recall Herring gulls. Wish I could remember what the back looked like.
I agree with Richard's 1st impression that your gull was a 2nd summer Am Herring Gull. In fact the bird in his post is virtually identical to yours!
The following features in your image are all good for Am Herring, but not for Great Black-backed:
Evenly proportioned jizz - GBBG would have a more protruding head & neck;
Unmarked lower wing coverts, particularly the axilliaries - these are usually quite checkered on GBBG & only the Yellow-legged Gull comes close in this respect;
Tail much too dark - GBBG tail band is usually much narrower with greater contrast with remainder of tail & tail coverts;
Even very young GBBG don't have the strong brown 'wash' across the belly, being rather cleaner & whiter in comparison to both Am & European Herring Gulls.
I also agree with Richard that, if the saddle colour is not visible as in your image, then dark primaries & primary coverts on the upper wing are extremely similar for a range of 2nd summer gulls species.
Cheers: Wayne
PS: If you lighten the image you will see the legs are definitely pink, so Lesser Black-backed Gull is ruled out too.;)