Foraging is one of the most fundamental behaviors for sustaining life. Yet, the drivers and effects of variation in foraging behavior are often not well understood. In this dissertation, I investigate both the causes of foraging choices – focusing on how the glucocorticoid stress response affects foraging – and the consequences of dietary variation in a declining aerially insectivorous bird, the tree swallow (Tachycineta bicolor).In Chapter 1, I explore whether glucocorticoids affect total activity and offspring feeding rate. Birds with experimentally elevated corticosterone (the primary glucocorticoid hormone in birds) were initially less active and fed their nestlings at lower rates than control birds. However, as the provisioning period progressed, experimental birds increased both measures of activity faster than control birds; by mid-provisioning, they had higher activity rates than control birds. In Chapter 2, I use fecal sample DNA metabarcoding to show that adult birds with experimentally elevated corticosterone had diets composed of a lower percentage of macronutrient-rich aquatic insects than control birds. Combined, the results of my first two chapters suggest that stressor-induced changes in foraging could be an underappreciated contributor to reductions in fitness and population declines. In Chapter 3, I test whether environmental conditions experienced during development affect the corticosterone response to challenges in adulthood, which might have downstream effects on foraging behavior. I found a strong, negative relationship between ambient temperature during early development (incubation) and an individual’s corticosterone response to stress later in life. In Chapter 4, I investigate the consequences of variation in the diets of tree swallow adults and nestlings. Nestling dietary diversity positively predicted fledge success; however, aquatic insect content, which was previously found to be a strong predictor of reproductive success in tree swallows, was not related to fitness or fitness-related metrics. In Chapter 5, I describe a bird biology outreach program I developed while a graduate student at Cornell University, outlining how we adapted the program for virtual instruction during the COVID-19 pandemic. I encourage others to explore similar outreach options to increase access to nature during the pandemic and beyond.