Dissertation Research: Biomechanics of Feeding in Loggerhead Shrikes

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It is well known that young birds succeed less often at catching food than do adults; this may be part of the reason that they frequently die during their first year of life. However, it is not clear whether this difference in feeding results from all young birds individually improving their feeding performance by learning over time, or whether adult birds are better feeders because all the physically or behaviorally deficient young birds die out at earlier stages, leaving only those that perform better to reach adulthood. The aim of this study is to distinguish among these possibilities in the federally endangered San Clemente Loggerhead Shrike (Lanius ludovicianus mearnsi), a predatory songbird endemic to San Clemente Island, California. The change over time of their prey capture, processing, and feeding performance will be measured using high-speed video imaging. Feeding performance has been directly linked to survival and reproductive success in other birds. This study will provide managers breeding shrikes in captivity in order to re-establish wild populations with objective criteria for deciding which individual shrikes are likely to feed themselves successfully if released, and at which stage of development. This study will also advance our theoretical understanding of why feeding performance improves with age, which physical and behavioral characteristics are important for successful prey capture, and how shrikes, as a group, have evolved their remarkable predatory capabilities. Finally, because the analytical techniques used for measuring feeding performance have distinct biomedical applications (e.g., kinesiology, exercise physiology, physical therapy), this project will also train undergraduate students who seek careers in medical, health, and wildlife professions.