Rossís Goose (Chen rossii)
Sorry, not convinced this one is a Ross's Goose - it's got the Snow Goose black 'grin' on its beak. Bit tricky to judge size here, any more photos of it?
believe me, it's a ross's. I've seen plenty of snows and this one was not much larger than a mallard! It was positively confirmed by our top birders.