Patterns of lake acidity and waterfowl communities

Breeding waterfowl communities were studied in 28 lakes in three areas in North Europe, along gradients of acid precipitation and alkalinity that result in lake conditions ranging from unaffected to strongly acidified. Acidic lakes had generally sparser and less complex vegetation, and fewer invertebrates were caught in activity traps. There was neither correlation between pH and waterfowl species richness (genus Anas, family Anatidae, and waterfowl sensu latu tested separately), nor between pH and waterfowl diversity (Simpson's index). Further, pH and waterfowl population density (genus Anas, family Anatidae, and waterfowl sensu latu) were not correlated, but when functional rather than taxonomic groups were considered, pH and relative abundance of fish-eating species (Gaviidae and Podicipedidae) were correlated. However, the relative abundance of Bucephala clangula, a diving duck that may compete with fish for food, was not correlated with pH. Although individual species may be affected, community level responses of waterfowl to acidity are either absent or hard to detect at our sites.