That is a herring gull if I am not mistaken and they will grab food wherever they can. Just ask people in Whitby who have fish and chips and they get mobbed by gulls who steal the meal from them.
Some years ago I was in Ullapool and was watching a harbour seal diving and coming up with a fish and because it was too awkward to swallow it threw the fish into the air, caught it and swallowed it whole. This happened a couple of times more, then the next time a herring gull who had obviously been watching, swooped at exactly the right time and when the fish was thrown in the air it grabbed it in its beak and flew onto the beach to eat it.