Despite its importance as a tool for understanding a wide range of animal behavior, the study of reinforcement schedules in the laboratory has suffered from difficulties in the biological interpretation of its findings. This study is an operant-laboratory investigation of the ability of European starlings, Sturnus vulgaris, to learn to respond adaptively to the problem of foraging on patchily distributed prey that are uncertainly located in space. In order to maximize the biological relevance of the laboratory study, variation in the aggregation of earthworms, Lumbricus terrestris (a prey species), was rigorously quantified from the field, and the experimental birds were presented with reinforcement schedules designed to represent the extremes of the observed variation. The results demonstrate that, even for a single prey species, the degree to which individuals are aggregated can vary markedly over a range of spatial scales, and that starlings can rapidly learn to respond, in an adaptive manner, to these variations. These findings suggest that starlings are capable of adjusting their behavior to facilitate the efficient exploitation of prey that occurs in patches of an uncertain nature, and thus illustrate the heuristic value of an ecologically informed operant-laboratory approach to studying foraging behavior.
Key words: optimal foraging, reinforcement schedules, operant behavior, prey distribution, spatial aggregation, patchiness, Sturnus vulgaris
The authors made a video tape showing starlings "probe foraging" for topsoil invertebrates among sheep. This is the ecological foraging problem described in their paper. The key thing to note is the alternation between continuous probing (i.e., approximately every step) and probing interspersed with walking or hopping or flying short distances.
You can view a brief selection (2,000K) from the video tape in Quicktime format. For best viewing, save a copy of this file to your own computer’s desktop, double-click on it and then change the image size in the player. Set the movie to “Loop” if possible. (See JEAB's Video Page for more information.)