Ecological compensation measures and breeding birds

From 1997 to 1999, we studied the effects of small plots for ecological compensation on breeding birds in 23 areas of 5 to 10 km² in the Swiss lowlands (total area 169 km²). The territories of 39 indicator bird species were recorded by territory mapping. 29 of them occurred in at least one study area with a low average of merely nine species per study area. Only three species bred in more than three quarters of the study areas. On average, 14 territories of indicator species were recorded per km². In grassland areas the number of species and of territories was considerably lower than in crop dominated areas. The territories of species breeding in hedges or in wet habitats were more often than expected close to sites for ecological compensation. By contrast, species breeding in open farmland were more distant from them than expected. The territories of species breeding in bushes or trees were preferentially in hedges or close to extensively farmed meadows designated as sites for ecological compensation. In territories of open farmland species, hedges and meadows were underrepresented. Our investigations indicate that the presently rather low biological value of the ecological compensation sites could be increased substantially by the new federal ordinance.