The bird population index is measured relative to population size in the year 2000 (i.e. the value in 2000 =
100).
Species for each group are standard across countries.
Source: European Bird Census CouncilThe bird population index is measured relative to population size in the year 2000 (i.e. the value in 2000 =
100).
Species for each group are standard across countries.
Source: European Bird Census Council