Limited attention: the constraint underlying search image

Recent models of predator search behavior integrate proximate neurobiological constraints with ultimate economic considerations. These models are based on two assumptions, which we have critically examined in experiments with blue jays searching for artificial prey images presented on a computer monitor. We found, first, that when jays had to switch between searching for two distinct prey types, they showed no reduction in detection rates compared to no-switching conditions, and second, that when jays divided attention between searching for two prey types at the same time, they had lower detection rates than when they focused attention on one prey type at a time. Our results suggest that limited attention strongly affects predator search patterns and diet choice, including the ubiquitous tendency to form search images.