Meeting Abstract
Loggerhead shrikes are medium-sized passerines that eat insects and small vertebrates. Previous work on their hunting behavior, morphology, and bite performance has demonstrated the importance of the beak and biting for killing and subduing vertebrate prey. However, little is known regarding the ontogeny of predatory performance, given the difficulties of observing predatory attacks in the wild. We studied the predatory kinematics of adult and juvenile San Clemente Loggerhead Shrikes, in association with a captive breeding and release program on San Clemente Island, CA. We present the results of a two-tiered analysis, focusing on (1) overall prey capture and handling efficiencies, and (2) 3-D prey-striking and biting kinematics. With regard to (1), we found that juveniles typically required longer handling times and delivered more bites to immobilize vertebrate prey, but used fewer prey-shaking movements than did adults, although the rates of these behaviors were similar between age classes. With regard to (2), we found that adults struck mice with greater average velocities than they did crickets, and that prey-striking and jaw-closing average velocities tended to be higher in juveniles than in adults when attacking crickets. Taken together, these results suggest that adults might rely on different strategies for immobilizing vertebrate prey (e.g., more on prey shaking, less on biting), and more appropriately match their attack velocities to the demands of their prey. Juvenile birds are known to under-perform relative to adults in foraging; these data suggest specific mechanisms by which this occurs in shrikes, and potentially other predatory taxa.
