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Individual and Environmental Effects on Foraging Performance in Nazca Boobies

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Reproductive senescence is common in seabirds; however, the underlying causes remain elusive. Because reproductive success and foraging performance of seabirds are often linked, a decline in foraging performance with age may underlie reproductive senescence. Environment, too, affects breeding, with high prey availability and/or quality improving reproductive outcomes. For seabirds, foraging, such as the flapping flight required to reach a foraging location, is physically demanding. Senescent decline in a seabird’s ability to match the costs of foraging might cap delivery of food to young at the nest, and provide a proximate explanation for poor breeding success in old age. I evaluated the relationship between age, sex, environment, and three aspects of foraging (flight, foraging, and diving performance) in a tropical seabird, the Nazca booby (Sula granti), on Isla Española, Galápagos, Ecuador. I predicted poor performance by old Nazca boobies compared to young or middle-aged adults, contributing to observed patterns of reproductive senescence in this species. Young adults may still lack the foraging ability of middle-aged birds, contributing to overall age-related variation in foraging performance. Biologgers (GPS in 2011–2012 / 2014–2016, GPS/accelerometer in 2015–2016) were deployed during the incubation period on male and female adults of young, middle, and old age classes that correspond to poor, peak, and senescing reproductive success, respectively. I tested the ability of age and sex to explain variation in flight performance (e.g., airspeed) in Chapter 2. In Chapter 3, I evaluated foraging traits (e.g., mass gained during a foraging absence) by age and environment, and in Chapter 4, diving performance (e.g., dive depth) was evaluated by age. Of the commuting flight traits linked to physiology, only airspeed varied with age. However, sex-specific patterns of aging emerged for foraging performance: only females incurred longer foraging absences, while males showed early-life improvement in flight speed. Age affected female diving traits, with younger females not diving as deep, and flapping slower when taking off from the water after a dive. These varied, but cumulative, aging results emphasize the need for studies to examine a large suite of traits to dissect complicated aging patterns in wild populations.
Early-life improvement
El Niño-Southern Oscillation
Howard, Jennifer Lynn (author)
Anderson, David J (committee chair)
Elliott, Kyle E (committee member)
Browne, Robert A (committee member)
Conner, William E (committee member)
Silman, Miles R (committee member)
2022-01-15T09:35:33Z (accessioned)
2022-07-14T08:30:13Z (available)
2021 (issued)
Biology (discipline)
2022-07-14 (terms)
http://hdl.handle.net/10339/99396 (uri)
en (iso)
Wake Forest University
Individual and Environmental Effects on Foraging Performance in Nazca Boobies

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