Limited attention: the constraint underlying search image

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