Trends and drivers of change in diving ducks

image of Trends and drivers of change in diving ducks

This report addresses changes in population size in five species of diving ducks breeding and wintering in the Baltic Sea. Declines in breeding Greater Scaup, Eider and Velvet Scoters on the Baltic coast are verified. Long-tailed Ducks and Eiders have declined in winter. Breeding Eiders have declined in Norway. Monitoring programs in all Nordic countries are partly inadequate for detecting changes in numbers of birds both in winter and during breeding, but large-scale trends appear reliable. The reasons for the declines observed are largely unknown. For breeding Eiders in the northern part of the Baltic Sea a change in predation regimes on the breeding islands may be important. If the negative trends are to be stopped, a deeper understanding of the drivers involved and better knowledge about the ecological status of the Baltic Sea food webs utilized by the diving ducks are needed.



Wintering populations of the focal species

We follow the delineation of the Baltic Sea (henceforth) wintering area by Skov. et al. 2011), including Kattegat and bordering the North Sea at the northern tip of Jutland, Denmark. This area may also be defined as the HELCOM area (see HELCOM 2013). The total area of the Baltic/ Wadden Sea flyway is, however, larger, including the Wadden Sea and other areas on the North Sea / Atlantic coast. Other areas (Norway, Iceland) are mentioned when appropriate. The wintering areas of Norwegian and Icelandic species are indicated as appropriate.


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