Phylloscopus collybita – SIFF-SAFF/SIFF SIAFF – Breeding summer visitor, passage migrant and winter visitor
The BTO winter atlas showed that Chiffchaffs were present in 41% 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 3 or more birds seen in a day.
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. 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.