Indirect risk effects reduce feeding efficiency of ducks during spring

Area of Science:

• Ecology
• Behavioral Ecology
• Wildlife Science

Background:

• Indirect effects of predator risk on prey behavior can significantly impact prey populations.
• Predation risk increases prey vigilance, reducing time for essential activities like foraging and potentially lowering foraging efficiency.
• Understanding predation risk effects is crucial as it influences the profitability of food resources based on environmental conditions and forager state.

Purpose of the Study:

• To investigate how ducks perceive predation risk across different habitat types.
• To determine the relative influence of perceived risk versus energetic demands on duck foraging behavior.
• To assess species-specific responses to predation risk and food availability.

Main Methods:

• Field study in Illinois, USA, manipulating food abundance in various wetland types.
• Focal-animal behavioral sampling of five duck species in treatment and control plots.
• Generalized linear mixed-effects models to analyze feeding intensity and duration in relation to vegetation structure and other factors.

Main Results:

• Mallards and blue-winged teal exhibited more intensive feeding and longer feeding stints in open habitats, suggesting higher perceived risk due to limited visibility.
• Wood ducks, nearing nesting, took greater risks for higher food rewards, indicating an increased marginal value of energy.
• Duck foraging behavior varied based on vegetation structure, with some species prioritizing energy gain over perceived predation risk.

Conclusions:

• Duck species value energy differently depending on surrounding vegetation structure and density.
• Increased marginal value of energy can be a stronger driver of foraging behavior than perceived risk.
• The perceived value of food is a complex interplay of energy content, environmental conditions, and the forager's physiological state.