The effects of urbanization on the avian gut microbiome

The gut microbiome influences and is influenced by the host, and can affect the host organism by contributing to health, development and immunity. Similarly, the host can influence this community; it’s makeup can vary with host species, locality, diet, social stressors, and environmental stressors. Some of these environmental stressors have arisen due to human-induced rapid environmental change, like urbanization. The physiology and behaviors of organisms that are able to persist in urban environments are often different from their non-urban congeners. Nutrition, development, and immunity—all of which are affected by the gut microbiome—are important factors that can determine survival in urban environments. Ecologists are therefore asking new questions about how an urban environment shapes gut microbial communities, and how the numerous services gut fauna provide affect host success in an urban context.

My dissertation research demonstrated that urbanization changes the bacterial communities of birds as well as provided correlational and experimental evidence for the biotic and abiotic traits driving these changes. Urban birds differed from rural ones by multiple measures. I also found evidence that noise pollution explains some variation in alpha diversity among urban and rural birds. Building upon this finding, I experimentally showed that the gut microbiome changes with exposure to noise, as does food intake and plasma corticosterone. However, contrary to my hypothesis, food intake and corticosterone were not the mediating factors between noise and the gut microbiome. All of this work was accomplished using noninvasive cloacal swabs to measure the gut microbiome, which my dissertation research found are reflective of the large intestine and capture individual variation in the microbiome. The work that comprised my dissertation will impact methods decisions in future microbiome studies in both free-living and captive birds. It will also contribute to the way we look at the relationships between host environment, host, and the gut microbiome, as well as influence how we think about urban ecology as a whole. Altogether, my dissertation research accomplished my goal to work in an emerging field at the interface of urban and microbial ecology.