At first I thought this was a Ring-billed, but wasn't sure; mightn't it be a third-winter California Gull? So I checked with an expert, Mike Rogers. Mike says no, it's a Ring-billed, classic second-winter (except for the absence of black in the tail-feathers, a variable character.) The bill is too short and the ring too perfect for 3W California, and the iris would be darker on a California.