Fig. 2. Mean population changes of habitat-defined bird species groups Mean
(standard error, SE) population changes farmland bird species in the Czech
Republic estimated from 1985–1989 to 2001–2003 expressed for groups of arable
land species, grassland species and species of shrub and trees. Population changes
were expressed at a common scale for all species from
2 to 2 (see Section 2.1 for
more details). Group means significantly different from each other are labelled by
different letters. Group means significantly different from zero are marked with an
asterisk. (a) All species (n = 34), (b) common species (n = 25). Note that the effects of
other predictors were controlled for.