Larus argentatus argentatus
This species had already increased considerably by 1894, and was then a common resident, and seems to have continued to increase steadily. There are colonies of varying size all along coastal cliffs and on the islands (eg 300 pairs Newport Head, 300 pairs Skokholm, 650 pairs Skomer - all in 1946)
R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society