Stercorarius pomarinus
Mathew makes the surprising statement that this "is by far the commonest of the family upon our coasts", and says a few are to be seen every autumn. It seems likely that he confused it with the Arctic Skua. It has not been seen Skokholm. J.Wynne records that he has seen it twice and Mackworth-Praed states one was shot in 1914. One was seen in Whatsands Bay, 21 Sept 1930 (D.L.Lack)
R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society