Optimal Diet Choice Contingency Model Hypothesis: Fitness Increases with Increase Individuals Long-Term Average Rate of Energy Gain Two Prey Types: Specialize or Generalize? Extend to > 2 Prey Types

Contingency Model Parameters: Encounter Rates I ; I = 1, 2 Net Energetic Gain e i Handling Time h i Prediction: Greater rate of Energy Gain

Contingency Model Specialize: Otherwise, Take Both Prey Types Specialize: High Density, More Profitable Prey Type, Increase Energy of Type 1, Decrease Handling Time of Type 1

Krebs, J.R. et al Anim. Behav. 25:30.

Thompson & Barnard Anim. Behav. 32:554.

Davies, N.B J. Anim. Ecology 46:37. Pied Wagtail: Profitability Predicts Prey Choice

Cantanhede et al Neotrop. Icthyol. 6 Predator-fish diet narrows after impoundment increases density of preferred fish-prey.

k (k > 2) Prey Types Given at least j types in optimal diet, add type (j + 1) if profitability of type (j + 1) exceeds current long-term mean rate of energy gain; otherwise, diet is optimal.

Hawkes et al Am. Ethnol. 9:379.