The BTO winter atlas showed that Wigeon were present in the majority of 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 300 birds seen in a day.
Over 2,000 within the Cleddau Estuary system constituted the main concentration.
Graham Rees