The Swiss agri-environment scheme promotes farmland birds: but only moderately

Abstract

Agricultural production is intensive in the Swiss lowlands, where about half of farmland bird species are on the Red List. A nationwide agri-environment scheme was launched in 1993 to improve biodiversity on farmland. To qualify for subsidies, farmers have to use at least 7% of their farmland as ecological compensation areas (ECAs). We evaluated the effect of the ECAs on three levels. The national Swiss Bird Index for farmland birds shows a decline from 1990 to 2004. On a regional level, we monitored breeding bird communities on 23 study areas twice, with an interval of 4 years. Endangered species were largely absent and species richness was low. Between 1998 and 2002 and 1999 and 2003, respectively, common species showed a slight increase, whereas endangered species continued to decline. On a local level, it was expected that ECAs would have an effect on density and distribution of bird territories. The percentage area covered by ECAs had no influence on the population density of open farmland indicators nor on landscape indicators. A stepwise forward multiple regression model showed that “ECA-hedges” were significantly more often occupied by indicator species than hedges not financially supported by the agri-environment scheme. The Common Redstart Phoenicurus phoenicurus is an indicator species of traditional orchards. It occupies large traditional orchards with a high percentage covered by ECAs within 50 m of the edges more often than in the absence of ECAs. In two experimental study areas, ECAs of high ecological quality covered an exceptionally high proportion of farmland. In Laconnex in south-western Switzerland, many species benefit from these extra ecological improvements not part of the official agri-environment scheme. The Whitethroat Sylvia communis for example increased more than tenfold within 12 years to an actual density of 12 territories/km2, Stonechats Saxicola torquatus reached more than 8 territories/km2 and the Melodious Warbler Hippolais polyglotta also showed a remarkable increase. In the experimental study area “Widen” in north-eastern Switzerland, Yellowhammer Emberiza citrinella and Red-backed Shrike Lanius collurio doubled in numbers between 1998 and 2003, but not in the control area. We conclude that ECAs do have some positive effects on the breeding distribution of selected indicator bird species. However, the effects are moderate which is due the low quality of the ECAs.