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When ice covered the bird sanctuary, tufted ducks (Aythya fuligula) sometimes rested on open water near Neuchâtel, the feeding ground of the Bas-lac region. Boat traffic for hunting, fishing, and sport was dense and produced major disturbances. For Vaumarcus and Yvonand, disturbances were similar but considerably greater than those of the bird sanctuary. Boat traffic was again the main sources of disturbance. Frequent storms forced fishermen to take in their nets at night, which greatly disturbed feeding ducks. These nocturnal disturbances were probably responsible for the decrease in the number of birds in the Bas-lac region. The duration of feeding activity was more or less constant throughout winter and the only increase was noted between the end of November and the end of December when boat traffic on the lake produced increased disturbance resulting in more flight activity that cost energy. On Lake Neuchâtel, the feeding area with the least disturbance was occupied first with the greatest number of wintering ducks. Movement of ducks towards other feeding areas was caused by disturbance at night.