And what on earth is this?

They look like some sort of turkey with webbed feet. This pair were living on a lagoon separated from the sea by a strip of scrub and pebbled beach. This is a National Trust reserve in Anglesey where they were providing breeding areas for sea birds. Their companions were the usual array of mallards and hybrids plus a mute swan who was very bad tempered. The sea birds were at the other end of the lagoon. They were huge birds and tame.