An avifaunal zonation of Switzerland and its relation to environmental

Abstract

1 We propose a quantitative zonation of Switzerland based on the distribution of breeding birds. We use a combined dataset from two nationwide bird censuses 20 years apart to account for distribution changes between the censuses. This approach approximates the 'potential' distribution of species more closely than a dataset from one period only. 2 A numerical approach with correspondence analysis and non-hierarchical clustering resulted in five avifaunal regions, consisting of two lowland regions north of the alpine arch, two alpine regions and one region of southern alpine valleys. 3 We identified characteristic species for each region using the indicator value analysis of Dufrêne and Legendre (1997) and determined environmental conditions separating the regions with discriminant analysis. 4 Our zonation partly corresponds with previous subdivisions of Switzerland, but has the advantage of being based on a numerical approach instead of expert knowledge. 5 We discuss avifaunal and ecological differences between the regions and relate our zonation to the classical biogeographic regions of Europe. Finally, we evaluate the importance of the zonation for bird conservation.