This is a Guillemot (Uria aalge), but this is the form known as a Bridled Guillemot, because of the white eye ring and small white line behind the eye. They are not considered as a subspecies, but as an example of Dimorphism. Put simply this is the existence of two distinctive forms of plumage within one species. Apparently in Britain the further north the colony, the more likely you are to find these.
