Blue Tit - 1980s winter

The BTO winter atlas showed that Blue Tits 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 70 birds.  

However, it should be noted that the figures show a high correlation with the number of recording cards returned (therefore related to recording effort) for each 10km square.  

Graham Rees