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.
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.
We identified characteristic species for each region using the indicator value analysis of Dufrêne & Legendre (1997) and determined environmental conditions separating the regions with discriminant analysis.
Our zonation partly corresponds with previous subdivisions of Switzerland, but has the advantage of being based on a numerical approach instead of expert knowledge.
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.