Long-term foraging optimization in northern shovelers

Abstract

In this paper I attempt to explain the seasonal foraging strategy employed by male northern shovelers ( Anas clypeata). Through the use of dynamic-optimization modeling I demonstrate that male shovelers are optimizing total foraging time over the entire summer by foraging heavily when resources (cladocerans) are abundant and utilizing endogenous reserves during times when resources are in short supply. Additionally, I construct predictive long-term models based on cladoceran dynamics and show that observed values for shoveler body mass and foraging dynamics agree with the models. Body masses of collected birds fit the predictions of the mixed (long-term I) model better than the long-term II model. However, both models underestimated total foraging time often by as much as 50% Long-term foraging optimization strategies apparently are more common in birds than previously thought and are determined by three ecological criteria: (1) degree of foraging specialization, (2) availability of preferred prey, and (3) physiological or behavioral constraints which allow for endogenous fat storage or exogenous caching of food items.