Fig 1) This is a tricky one. It looks a lot like a Thayer's Gull. Only it's as large as the nearby Herring Gulls. The bill has a lot of pink in it, and it's quite long and straight. The color of the bill and its shape points us away from Thayer's or a hybrid with Glaucous-winged and toward Nelson's Gull. Notice the bulbous bill of the Glaucous-winged Gull in the rear left.

Fig 2) In flight, it's essentially like a Thayer's Gull.

Fig 3) This amount of marbling at the bases of the retrices exceeds what is possible (I would think) of Herring and Herring x Glaucous-winged. Some Thayer's can show tails like this.