Environmental changes and population trends of breeding waterfowl in northern Baltic Sea

Abstract

Causes behind the changes in waterfowl populations in the Archipelago Sea, SW Finland, have until now not been quantitatively analysed. We modelled the impact of eutrophication, winter severity, weather conditions during breeding and water salinity on the breeding populations of ten waterfowl species (ducks, great crested grebe Podiceps cristatus and coot Fulica atra) using generalised linear models and the program TRIM (TRends and Indices in Monitoring data). The populations of the goldeneye Bucephala clangula, coot and velvet scoter Melanitta fusca decreased with increasing eutrophication. The populations of the goldeneye, coot, mallard Anas platyrhynchos, mute swan Cygnus olor and eider Somateria mollissima were most vulnerable to winter severity. We did not find evidence for impacts of weather conditions during breeding or water salinity on population trends. We also discuss alternative explanations to the observed population trends, such as predation and disturbance.