Larus fuscus graellsii
"A common resident. Not so numerous as the Herring Gull" - Mathew, who says it bred 1894 in colonies of only 20-30 pairs, and if this was correct, it has increased considerably since. In 1946 approx 800 pairs were breeding Skokholm, and 1000 pairs Skomer. Breeds also Caldey, St Margerat's, Ramsey and islants, Sheep Island, and some mainland cliffs (eg Pwll Deri)
R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society