Condition-dependent foraging strategies in a coastal seabird: evidence for the rich get richer hypothesis

Abstract The degree to which foraging individuals are able to appropriately modify their behaviors in response to dynamic environmental conditions and associated resource availability can have important fitness consequences. Despite an increasingly refined understanding of differences in foraging behavior between individuals, we still lack detailed characterizations of within-individual variation over space and time, and what factors may drive this variability. From 2014 to 2017, we used GPS transmitters and accelerometers to document foraging movements by breeding adult Brown Pelicans (Pelecanus occidentalis) in the northern Gulf of Mexico, where the prey landscape is patchy and dynamic at various scales. Assessments of traditional foraging metrics such as trip distance, linearity, or duration did not yield significant relationships between individuals. However, we did observe lower site fidelity and less variation in energy expenditure in birds of higher body condition, despite a population-level trend of increased fidelity as the breeding season progressed. These findings suggest that high-quality individuals are both more variable and more efficient in their foraging behaviors during a period of high energetic demand, consistent with a “rich get richer” scenario in which individuals in better condition are able to invest in more costly behaviors that provide higher returns. This work highlights the importance of considering behavioral variation at multiple scales, with particular reference to within-individual variation, to improve our understanding of foraging ecology in wild populations. Within-individual variation in foraging behaviors is not well-understood, despite historical appreciation of between-individual differences. Spatially explicit assessment of foraging strategies in Brown Pelicans revealed no consistent between-individual differences, but considerable within-individual variation. Birds in better condition had lower site fidelity and less variable energy expenditure, suggesting more efficient foraging despite uncertainty associated with this strategy. This is consistent with a “rich get richer” scenario and highlights the importance of considering behavioral variation at multiple scales.