Seasonal and Diel Changes in the Feeding Behaviour of Some Dabbling Duck Species on a Breeding Lake in Northern Sweden

The feeding behaviour of European Wigeon, Teal, Mallard and Pintail was studied in May, June and August on a shallow lake in northern Sweden at 660N. Duck behaviour was found to be related to the time of the day, the weather conditions and the food resources. In May, the dominant food resource was Chironomidae imagines, which were either present on the aquatic vegetation, or on the water surface. The food-seeking behaviour of Wigeon, Teal and Mallard was at that time almost exclusively restricted to the water surface or above it, while the Pintails also fed below the surface. In June, the Chironomidae imagines were still present but in greatly reduced numbers. The Wigeon and Teal now also fed to some extent below the water surface, whereas for Mallard and Pintail this type of feeding behaviour was dominant. In August, the Chironomidae imagines had all disappeared, but their larval biomass on the lake bottom had increased. The Wigeon still fed predominantly on or above the water surface while all the other duck species now almost exclusively fed below it. In June cold and windy weather induced Teal and Pintail, but not Mallard, to feed more frequently below the water surface, although such weather conditions in May and August did not lead to any drastic changes in the feeding behaviour of any duck species.