Breeding Waterfowl Populations in Northern Fennoscandia

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Abstract
The sizes of breeding populations of Anatidae, their distribution patterns, habitat requirements, annual fluctuations, etc. in the northernmost parts of Finland, Norway and Sweden were studied in 1972-1976 using aerial survey methods. The efficiency of aerial surveys was tested by comparisons between aerial surveys and simultaneous ground counts in small areas, such studies being undertaken in several different regions. The efficiency varied from 13.0% in Anas crecca to 100% for Cygnus cygnus. Dabbling ducks in general had much lower efficiency than diving ducks. Habitat data were obtained from topographic maps and from geological survey maps. During the flights photographs were taken on representative lake types in the squares and additional data were recorded. All waterfowl observations were recorded on tape in the following categories for each species: single pairs, single drakes or females, males in flocks and other flocks. Criteria for breeding pairs were: pair, males single or in groups of 2-5 and in some cases lone females (Bucephala clangula in late surveys). The total breeding population of Anatidae was 155,610 pairs, about 68,000 pairs each were found in Finland and Sweden, whereas 20,500 pairs were estimated for the part of Norway included in the survey. The populations of the different species were Anas platyrhynchos 19,270 pairs, A. crecca 25,000, A. querquedula 120, A. penelope 21,000, A. acuta 3600, A. clypeata 160, Aythya marila 1160, A. fuligula 25,530, Bucephala clangula 26,730, Clangula hyemalis 3430, Melanitta nigra 2750, M. fusca 1400, Mergus serrator 10,600 M. merganser 6630, M. albellus 280 and C. cygnus 769 pairs (about 30% breeding with nest). Population densities, vegetation and climate effects were examined. The impact of various forms of exploitation on the breeding waterfowl populations in northern Fennoscandia was discussed. The plans for extensive drainage of mires might impose a serious threat to the populations of some species.

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