| Summary: | In the face of global environmental change, the ability to predict adaptation has become a priority. To make predictions of adaptation, we must understand how environmental factors shape phenotypic expression, natural selection, and genetic variation. In my dissertation, I explore the effects of natural and experimental environments on phenotypes, selection, and genetic variation using pedigrees, nestling growth traits, and nestling survival data from three long-term seabird monitoring programs. In most chapters, I focus on a Northeastern Pacific population of black-legged kittiwakes Rissa tridactyla. First, I review weather conditions' various impacts on nestling avian growth. Next, I use a sliding window approach to analyze three long-term seabird datasets. I use these analyses to identify specific periods of environmental variation that correlate with nestling growth, assess changes in environmental predictors across years, and predict future nestling growth under climate change. My findings reveal specific breeding season periods that are strongly associated with variation in nestling growth. These associations suggest warmer conditions may result in poorer growth for two of the three species studied. Further, windows of environmental influence changed between historical and contemporary periods, emphasizing the need to investigate how such changes might affect adaptation to changing environments. In my final chapters, I use data from a kittiwake food supplementation experiment to examine the relationship between food conditions, the variability of selection strength, and variance components of nestling kittiwake size traits. I find that natural selection is strongest in early ontogeny, in non-food supplemented nestlings, and for the youngest nestlings in a brood. Selection magnitude varied among years, but annual variation in magnitude was similar for all treatment and hatching order groups. Warming conditions have mixed effects on selection that depend on food supplementation and hatching order. Finally, I ...
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