Larus argentatus – GWYLAN Y PENWAIG – Breeding resident and winter visitor
The BTO winter atlas showed that Herring 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 400 birds.
All squares were used for feeding purposes but the largest concentrations were at coastal roost sites
Data collected by volunteers for the BTO. Lack, P. 1986 Atlas of wintering birds in Britain and Ireland. T & A.D. Poyser.