We finish with a large, long-billed gull which looks like it is about to take off from a beach. You will notice straight away that it is largely pale brown, which should tell you we are not dealing with an adult gull. Perhaps less obvious, but vital in the identification, is that there are no obvious black tones in the plumage (the tail is in shadow, so is tonally unreliable), and particularly in the tips of the wings. All immature big gulls have dark in their wings apart from Glaucous and Iceland Gulls. Both of these northern birds have similar plumages at each age group (which is juvenile here). Structure is the easiest way to identify one in isolation. The bill is the best clue here: long and deep and pink with a black tip: classic juvenile Glaucous Gull.
Big gull structure and shape
Pale coffee-coloured plumage all over
White flight feathers; no black in wings
Long pink bill with black tip
Long, pink, black-tipped bill Pale coffee plumage Wings lacking any black feathering