Larus marinus – GWYLAN GEFNDDU FWYAF – Breeding resident
The BTO winter atlas showed that Great Black-backed Gulls were present in most 10km squares during the winters of 1981-82, 1982-82 and 1983-84.
The darker the colour, the higher the relative total count for each 10km square. The darkest blue represents over 60 birds, being concentrated in squares SM 80 & 81.
Graham Rees (County bird recorder 1981 to 2007)
Data collected by volunteers for the BTO. Lack, P. 1986 Atlas of wintering birds in Britain and Ireland. T & A.D. Poyser.