The Effect of Wing-Flashing Behavior on Prey Capture Performance of San Clemente Loggerhead Shrikes.

Abstract

Loggerhead shrikes (Lanius ludovicianus) are medium-sized predatory songbirds that feed on arthropods and vertebrates. Prior to attacking their prey, shrikes have been observed performing "wing-flashing" behavior, consisting of rapid fluttering of the wings that seems to emphasize the white patches on their dorsal surfaces. We sought to quantify this behavior by analyzing videos of San Clemente loggerhead shrikes attacking insect and vertebrate prey, to understand whether and how wing-flashing affects prey capture performance. We measured predictors of wing-flashing behavior, wing-flashing kinematics, and prey capture performance in terms of the number of strikes required to kill prey, prey strike durations, prey escape distances, and prey survival probabilities. Juveniles were more likely to perform wing-flashing behavior than adults, and lizards elicited wing-flashing more than mice and crickets. Adult males tended to flash their wings faster than juvenile males, and although wing-flashing rates were similar between ages for females and across prey types (∼15 Hz), shrikes flashed their wings for longer durations toward lizards. Wing-flashing was generally associated with fewer strikes to kill prey and resulted in longer prey strike durations for adult shrikes, longer prey escape distances, and lower prey survival probabilities for male shrikes. Our results suggest that wing-flashing behavior of loggerhead shrikes enhances their prey capture performance, possibly by stimulating prey to move-and not to move, depending on prey type-making them more vulnerable to predatory strikes.