Great Northern Diver - 1980s winter atlas

The BTO winter atlas showed that Great Northern Divers were present in some coastal 10km squares and the outermost part of the Cleddau Estuary, 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 3-5 birds.
Graham Rees