Chlidonias leucopterus – Cors-wennol Adeinwen – Rare visitor.
White-winged Black Terns breed in Poland and Russia, from where they depart between August and early October, small numbers occurring annually in Britain (Cramp 1985). In Pembrokeshire, the first was recorded at the Gann on 31 August 1973 (K.J.S. Devonald), followed by singles at Llysyfran reservoir on 16-28 October 1976, Llanstadwell on 26 August 1986 and Skokholm on 3 September 1990.
CRAMP, S. (ed.) 1977-1993. Handbook of the birds of Europe, the Middle East, and North Africa: the birds of the Western Palearctic. Oxford, Oxford University Press. 7 Vols.