Foraging strategies of granivorous dabbling ducks wintering in protected areas of the French Atlantic coast

Most important day-roosts for wintering ducks are protected, but the use of such sites as foraging habitats by Anatidae has received little attention. We studied the foraging activity of wintering mallard (Anas platyrhynchos) and teal (A. crecca) at four protected areas of the Marshes of Rochefort, western France. These species are generally nocturnal feeders, but they may expand their foraging time into the daylight hours if they have high energy requirements. Our goal was to identify the factors that lead dabbling ducks to increase their daily foraging time, so that the management of protected sites used by ducks diurnally could be adjusted accordingly. We demonstrate for the first time that, at the holarctic scale, granivorous ducks in colder habitats have longer diurnal foraging times. In western France, foraging represented 37-60% of ducks' daily time-budget: 16% of daylight hours and 85% of the night were spent foraging on average. Teal (350 g) fed longer per day than mallard (1100 g), and this seemed to result from different migration strategies rather than differences in body mass. This study suggests that management of protected areas should be adjusted to the climatic conditions of a wintering quarter and to the migration status of species in the duck community, so that adequate foraging sites are available for energetically stressed individuals to fulfil their daily requirements.