Variability in behavioural response of wintering black ducks to increased energy demands
We observed black ducks (Anas rubripes) wintering at three sites differing substantially in food quality (energetic value) and quantity to determine what environmental factor(s) influenced changes in behaviour and whether those changes functioned to balance energy demands with supplies. All behaviours other than preening showed some variation in response to environmental factors, with temperature consistently explaining the greatest amount of that variation. However, the ducks' response to cold temperature was not consistent between sites. For example, at colder temperatures, ducks at one site increased foraging, at another site they decreased foraging, and at the third site foraging remained constant. Apparently, one can only predict the specific response of ducks to increased energetic demands, i.e., colder temperatures, by knowing the quality and quantity of food available in addition to the cost of foraging.