Gavia immer – TROCHYDD MAWR – Winter visitor and passage migrant. Recorded in every month
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. Pembrokeshire County Bird Recorder 1981-2007
Data collected by volunteers for the BTO. Lack, P. 1986 Atlas of wintering birds in Britain and Ireland. T & A.D. Poyser.