Searching in patches by European starlings, Sturnus vulgaris

Despite the importance of within-patch search for predicting optimal patch-leaving strategy, little experimental effort has been devoted to the study of this foraging behaviour. In addition, predators' strategic responses to variability in features like the within-patch distribution of prey can have important consequences for their dietary decisions. We therefore analyse the search paths of European starlings, Sturnus vulgaris, foraging individually in artificial patches that vary in the spatial distribution of buried prey in an outdoor aviary. The results demonstrate that the birds are searching differently depending on the order in which the experimental patch-types are experienced. We speculate that where the spatial predictability of prey is initially high the birds adopt a fixed search rule that results in area-concentrated search once a prey item is found, and performs well for both distributions encountered. However, where the predictability is initially low a more flexible strategy is adopted that results in increased area-concentrated search with experience of a patch type, independent of the actual within-patch distribution of prey. These findings suggest that starlings can use distinct strategies for different prey types, but they are classifying these types on subjective criteria that are difficult to predict from a priori reasoning. (C) 1997 Elsevier Science B.V.