Worth the Reward? An Experimental Assessment of Risk-taking Behavior in Foraging Ducks

The way predators influence prey behavior is central to many components of basic and applied ecology. Foraging ducks face a fundamental tradeoff between food consumption and predation risk. Factors that influence ducks’ perceived predation risk or valuation of energy may affect how they approach this tradeoff. We manipulated food abundance in wetlands differing in vegetation structure to assess the merits of life history theory, perceived predation risk, and energetic demand in explaining how much risk five duck species during spring migration were willing to engage in while foraging. We found some evidence consistent with our life history prediction; species with a faster life history strategy were willing to engage in riskier behavior, by feeding more intensively, for a greater food reward. Mallards (Anas platyrhynchos) and wood ducks (Aix sponsa) exhibited risk-taking behavior consistent with perceived predation risk. Mallards devoted more time to feeding when in areas with less cover indicating that they perceive open habitats as safer. Wood ducks devoted more time to feeding in treatment plots, when in shallow areas, and larger flocks. Wood ducks exhibited behavior that was also consistent with an increase in energetic demand as observed by an increase in the proportion of time devoted to feeding later in the spring as they approached nesting. Habitat management for nonbreeding ducks typically focuses on providing large quantities of high quality food. We demonstrate that habitat structure can limit the efficiency with which ducks exploit this food resource due to perceived predation risk. Furthermore, we found that the way ducks balance the risk-reward tradeoff while foraging is dependent on a variety of factors and different for different species.