Food patch depletion by ruddy ducks: foraging by expectation rules

Abstract

The foraging behavior of six ruddy ducks (Oxyura jamaicensis) was studied in a large concrete and glass aquarium to determine if they used either a number or time expectation rule to decide when to leave a patch of food. Nine trials were conducted in which the prey density in each of two food patches remained constant for three consecutive trials and then was changed. If the foraging ruddy ducks were using an expectation rule to determine when to leave a patch, then the time spent in the patch (time expectation) or number of prey consumed from the patch (number expectation) should not change with a change in patch quality. The results of this experiment were not consistent with the predictions of either the time or number expectation rule. Thus, ruddy ducks appear to use some other measure to determine the appropriate time to leave a food patch.