Stercorarius crepidalus
This is a smaller species, to be at once recognised in the adult, by the two long and pointed central tail feathers. It is more scarce on our south-western coasts than the Pomatorhine Skua, but a season rarely passes without one or two being noticed. Sir Hugh Owen has shot an immature bird at Goodwick. There are two well-marked varieties of this species, one with a white breast and underparts, the other black all over, and in the black birds the blackness differs in its intensity, in some being of a rusty colour, in others of a deep coal black. The two varieties freely interbreed, the result being birds of a mottled plumage. We have seen examples pied black and white, the patches of the two opposite colours being symmetrically placed, and giving to the birds a very peculiar appearance