It's known that 1st cycle gulls typically show pointed primary tips, while older gulls display more rounded tips to the primaries. Looking at this bird's primaries, it seems they are rounded, but overall the plumage appears to be that of a 1st cycle gull. The caveat here is that the apparent shape of the primary tips can change with the bird's posture, behavior, and even the angle at which we observe these feathers. This is indeed a first cycle gull, but what species?
Proportionally, the body-to-head and body-to-tail size seem to rule out a large species (such as Herring, etc.). The barred tail, brown and white wing coverts, and mostly white neck narrow this down to Ring-billed Gull or Mew Gull. This next photo should help:
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Notice how the tips to the primaries appear more pointy now. But much more importantly, notice the pale edging surrounding the primary tips - a very "Mew-like" feature. This neat, white-winger-like edging is rarely as extensive in Ring-billed (see a typical 1st cycle Ring-billed example here). Additionally, the petite bill, domed head, smudgy hind-neck markings, and relatively dark gray 2nd generation scapulars all add up to a 1st cycle Mew Gull. There are several other field marks that help eliminate Ring-billed, but the description I've provided here should suffice. This Mew Gull was photographed in Seattle, Washington in January 2010.