Vigilance and scanning patterns in birds

We present a new approach to the analysis of scanning patterns in feeding birds. We estimate the probability of a bird detecting a predator from the frequency distribution of inter-scan intervals and the proportion of time spent scanning. This method avoids, several unrealistic assumptions implied in earlier analyses of vigilance data, and can accommodate predators attacking randomly or using prey behaviour to time an attack. The practical application of this approach is illustrated using data for feeding and vigilance in the ostrich (Struthio camelus). The analysis is discussed with reference to the hunting tactics of predators and Pulliam's (1973) model of feeding and vigilance in birds.