In urban habitats animals face unique challenges to survival and reproduction, including disturbance from human activity and noise. Thus, in urban environments only species or individuals with a particular suite of traits may persist. Therefore one of the major challenges is to understand how human expansion and increased urbanization impacts other animals. Further there is not only the impact of urbanization but also the fact that levels of activity vary with in different urban areas, such as city centers being very active while other areas my present refuges from urban activity. The goal of this study is to determine the successful utilization of these different urban regions based upon response to stress, as measured by stress hormone levels. The hypothesis being that species which are better able to handle stress are more likely to be able to occupy urban areas with high levels of activity. These researchers will examine stress response and measure reproductive success in the song sparrow based upon location relative to urban environments. The proposed research will provide STEM research experiences for under-represented minorities and inner city students. The work provides the unique opportunity to bring science and the lab to the urban environment.
Overview of Research: Urban environments pose unique challenges to animals, including disturbance from human activity and noise. Nevertheless, even within the busiest city, non-human denizens persist. These city-dwelling animals may be different in key ways from animals of the same species living in less disturbed habitat. In other words, city-dwellers may have evolved physiological or behavioral characteristics that allow them to avoid potentially deleterious effects of disruptive human behaviors. In vertebrates, one physiological mechanism that may be evolutionarily or plastically modified to promote persistence of organisms in urban environments is the adrenocortical stress response, which involves release of steroid hormones known as glucocorticoids from the adrenal cortex. The primary glucocorticoid in birds is corticosterone. Actions of glucocorticoids at baseline levels may aid animals in persisting in urban areas by stimulating glucose metabolism and promoting foraging activity. Thus, elevation of baseline glucocorticoids may be beneficial to city-dwelling birds. On the other hand, high baseline glucocorticoids may also reflect pathology resulting from the frequent occurrence of stressful events, which may overwhelm an animal’s internal coping mechanisms. Indeed, high glucocorticoid concentrations may result in increases in oxidative stress, and declines in body condition and survivorship. Elevation of glucocorticoids above baseline concentrations commonly aids animals in evading life-threating situations, such as predation risk. However, frequent activation of the stress response by human disturbance may lead to health problems associated with elevated glucocorticoids. Thus, the costs of mounting a large stress response in the city may outweigh benefits. We studied whether male song sparrows (Melospiza melodia) breeding in the city display differences in baseline or elevated glucocorticoids as a function of disturbance level. In addition, noise may interfere with animals via direct disturbance, by altering physiological processes, or interfering with communication. Thus, we also evaluated whether noise from human activities was related to differences in stress physiology. Finally, to more comprehensively examine how well song sparrows cope with human perturbation, we explored whether a number of condition metrics related to disturbance levels. To meet our research objectives, we captured male song sparrows in Riverside, California, measured the stress response by taking serial blood samples following capture stress, and assessed condition via morphological measurements, feather sampling, and a plasma antioxidant assay. Results and Intellectual Merit: Relative to individuals breeding in less disturbed areas, male song sparrows breeding in highly disturbed areas had lower levels of stress-induced corticosterone, and tended to have lower stress responses (measured by the difference between elevated and baseline corticosterone). Further, compared to individuals occupying less disturbed territories, male song sparrows that maintained territories in busier areas did not differ in body condition or antioxidant levels. In addition, males breeding in highly disturbed areas had higher quality feathers than males breeding in less disturbed habitat, suggesting better condition at molt. Thus, although other explanations are possible, our results suggest that song sparrows are an urban adapted species, and that suppression of the adrenocortical stress response in urbanized areas may aid in the maintenance of reproductive activity and health. Our research contributes to a growing suite of studies that examine variation in the adrenocortical stress response and other physiological condition metrics with respect to urbanization. As a whole, this body of research suggests a variety of responses to anthropogenic disturbance. Thus, to forward conservation efforts and advance our understanding of evolution in urban environments, future research should focus on identifying species-specific characteristics, such as differences in cognitive ability or ecology, which may determine particular responses to urbanization. Broader Impacts: Research on the effects of anthropogenic disturbance on birds offers a poignant opportunity to involve citizens and students in research. Awakening appreciation for human impacts on other organisms heightens awareness of the lives besides our lives, which exist even in highly urbanized settings, but which are invisible to most. We studied song sparrows in the immediate vicinity of the University of California, Riverside (UCR), providing us with a unique opportunity to engage undergraduate students in research, awaken students to the presence of our avian neighbors, and stimulate their interest in science. UCR is a Hispanic Serving Institution, serves a high proportion of first-generation college students, and has a highly diverse undergraduate student body. We recruited a number of undergraduates to participate in our research, including six women, three students of Hispanic origin, and one Asian American. Although experience for undergraduates in research is not difficult to acquire at UCR, these students were offered the rare opportunity to participate in a field study and to learn avian research techniques. In addition, students were introduced to Raven Pro, a powerful acoustical analysis tool, and gained data analysis skills.
