here - is a snow goose, not an escaped farmyard goose or a white variety of the greylags with which it's living. The snow goose is Chen caerulescens while the greylag is Anser anser. The snow goose is at home in North America, Greenland and northeast Siberia, but is an occasional visitor to the British Isles - though there are reported to be resident flocks on Coll and Mull.
Our snow goose is still around. This picture was taken as a flock of about twenty greylags fed in a field in Ormsaigbeg this morning. Sadly, while we're very excited about the presence of such a beautiful bird, the snow goose isn't popular with the greylags: they peck at it if it comes near them. But when the flock rose into the air, the snow goose went with them, albeit flying at a slight distance from the rest.