Wintering diving duck populations and available food resources in the Baltic

Abstract

The wintering populations of diving ducks in the Baltic in 1969-1973 are estimated on the basis of the data gathered during the International Waterfowl Counts and from some other sources. The calculated food consumption of these diving ducks in different parts of the Baltic and in the entire Baltic are compared with published information about the abundance and production of suitable food animals, especially Mytilus edulis. Some data on the consumption of food in Swedish study areas are discussed. The wintering diving ducks use a rather small proportion of the available food resources. Calculated for the entire Baltic the consumption by the diving ducks in winter amounts to 6.6% of the annual production of Mytilus in shallow water (depth less than 20 m) if the entire consumption is taken out as Mytilus. This compares to about 1% of the primary production of these areas.