Ecological Zoogeography of North European Waders, or Why Do So Many Waders Breed in the North?

Abstract

tative censuses (4900 observations on 26 wader species). Most variables used to describe latitudinal gradients have their maxima in the north: number of species, proportion of wader species in the land bird fauna, density of waders and proportion of wader density, biomass of waders and proportion of wader biomass, and energy demand of waders and proportion of total energy demand. No trends were observed in species diversity (Shannon function), while the evenness of the species-abundance distribution decreases northwards. The patterns can apparently be explained by effects of habitat heterogeneity: presence of seashore and mountain habitats increase numbers of wader species by 5-6 and 2-3, respectively, while species richness on peatlands is known to increase northwards at least partly due to habitat complexity. The high productivity (e.g. dipterans) of temporary shallow waters during the hatching period of the birds may also contribute to the northward increase in density and number of species of waders. North European waders could be grouped ecogeographically in five distribution types, which correlated well with the faunal types of the species.