An avifaunal zonation of Switzerland and its relation to environmental conditions

1 We propose a quantitative zonation of Switzerland based on the distributi on of breeding birds. We use a combined dataset from two nationwide bird ce nsuses 20 years apart to account for distribution changes between the censu ses. This approach approximates the 'potential' distribution of species mor e closely than a dataset from one period only. 2 A numerical approach with correspondence analysis and non-hierarchical cl ustering resulted in five avifaunal regions, consisting of two lowland regi ons 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 Dufrene & Legendre (1997) and determined environmental co nditions 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 e xpert knowledge. 5 We discuss avifaunal and ecological differences between the regions and r elate our zonation to the classical biogeographic regions of Europe. Finall y, we evaluate the importance of the zonation for bird conservation.