Effects of Human Disturbance on Physiology, Behavior, and Ornamentation in the Eastern Bluebird

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Gillespie, Lauren Marjorie
bluebird; ornament; testosterone; corticosterone; human disturbance; Animal Sciences; Biology; Ornithology
thesis / dissertation description
Overall, few studies have focused on anthropogenic disturbance on wildlife physiology. Research has typically focused on how environmentally contaminated areas or anthropogenic disturbance (e.g. noise, human activity) influences biodiversity, community structure and behavior of individual animals. However, understanding how disturbance influences some aspects of physiology can require sacrifice of the animal, prohibiting ecologically relevant measures of behavior and reproductive success. This research strives to examine covariation between testosterone (T) and corticosterone (CORT), plumage ornamentation, and behavior in two populations of eastern bluebirds (Sialia sialis) that differ in degree to which their habitat is modified by human activity.In this research I compare bluebirds breeding in a suburban golf course with those breeding at a rural site exposed to lower levels of human disturbance. I demonstrate that golf course females lay eggs later, produce smaller clutch sizes, and golf course pairs fledge fewer offspring. Males at the golf course population respond to live, conspecific intrusion with lower T levels and less aggression, and are more highly ornamented compared to a more rural population. Moreover, within the golf course site, but not the rural site, I found that males show an increase in T from nest building to incubation. Females at the golf course respond to live, conspecific intrusion with higher raw T and less aggression, and are more highly ornamented than the rural population. Females from both sites increase T and CORT from nest building incubation, however, aggression is not correlated with T. Results imply that golf course females cannot elevate T and display behavioral aggression. Lastly, golf course pairs take longer to complete nests and display increased nest attendance while golf course females only provision nestlings at significantly higher rates. Results here demonstrate support for the hypothesis that level of human disturbance subtly impacts behavior and physiology in bluebirds. This research adds to a growing body of literature stressing the importance of investigating physiological measures of disturbance in wild populations that are experiencing realistic selection pressures