The BTO winter atlas showed that Sparrowhawks 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 3 birds seen in a day.
It is likely the highest counts plotted reflected the maximum intensity of observer activity.
Graham Rees