We tested the predictions of an optimal foraging model using five captive great tits as predators. The birds were presented with two prey types, profitable and unprofitable, on a moving belt. Both prey types were made out of mealworms. When the encounter rate with both prey types was low, the birds were non-selective, but at a higher encounter rate with profitable prey, the birds selectively ignored the less profitable type and did so irrespective of the encounter rate with them. These results are as predicted by the model, but the birds did not as predicted change from no selection in a single step. We suggest that this is because birds invest time sampling to determine the availability and profitability of different prey types.
optimal foraging, great tit (Parus major)
Krebs, J.R., J. Erichsen, M. Webber and E.L. Charnov. 1977. Optimal prey selection in the Great Tit (Parus major). Animal Behaviour 25:30-38