I once thought I could identify most of the gulls, at least in my home area. More recent experience has cast doubt on that. This bird I had originally identified as a Herring Gull, but the smallish bill, steepish forehead, and darkish eye make me think now it is a Thayer's Iceland Gull. The photo was taken 25 March 2011 in Palo Alto, California, USA. I would appreciate any thoughts people might have about it.