Seagulls are notoriously difficult birds to ID, even for experienced birders, which I’m not. I think this is a Thayer’s Gull, but there’s probably about a 50% chance I’m wrong. Not being able to see the color of its legs removes one clue. Thayer’s Gulls are fairly common winter visitors in the Puget Sound region.
Photo taken in November 2014 at the beach in Edmonds.