Urbanization's Effects on Avian Morphology, Hormones, and Behavior Across Ontogeny

As the human population continues to grow at an unprecedented rate, anthropogenic changes are rapidly altering the remaining natural areas of the world. Urban-related stressors, such as lower food availability, the urban heat island, artificial light at night, and other pollution directly impact urban wildlife biodiversity and fitness. How wildlife cope and adapt to these urban modification's vary, depending on species, natural history, and location. However, most studies report differences in the urban phenotype, mostly in behavior, phenology, physiology, and morphology. While knowledge of phenotypic shifts in urban wildlife is growing, understanding the particular ecological pressures driving these changes and the mechanisms leading to phenotypic change and ultimately survival, is still lacking. Therefore, it is critical to understand how urbanization and its unique environmental factors affect the wildlife that reside in our cities. This dissertation is a multifaceted investigation of the impacts and mechanisms of urban ecology and evolution, in which I: 1) investigated behavioral, morphological, and physiological phenotypic shifts of an urban bird across ontogenetic stages (Chapters 1, 2, and 3); 2) highlighted the role maternal hormone transfer may play as a mechanism for urban adaptation (Chapters 2 and 3); and 3) directly tested the effects of limiting food, one of the most prominent urban challenges, on shaping morphological and physiological traits through a field manipulation experiment (Chapter 3). We were able to show clear phenotypic shifts in urban birds, including reduced incubation behavior, reduced masses and condition of eggs, nestlings, and adults, and elevated physiological glucocorticoid levels in nestlings and adults. Additionally, we showed that maternal hormone transfer across multiple endocrine pathways differs across an urban gradient with elevated maternal deposition of corticosterone and testosterone and reduced deposition of maternal thyroxine concentrations in urban yolks. Lastly, we provide experimental evidence that limited food, i.e. , reduced insect abundance, in urban environments is likely the urban ecological pressure driving these differences in morphology, maternal hormone transfer, and physiological responses in an insectivorous urban bird. This dissertation advances our understanding of how urbanization and its unique challenges affect urban wildlife and pinpoints a specific aspect of the urban environment where conservation management can implement actionable changes.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctorate Degree

Grantor

University of Nevada, Reno

Year dc:date.issued

2024

Author dc:creator

• Heppner, Jennifer J.

Advisor dc:contributor.advisor

• Ouyang, Jenny

Committee members dc:contributor.committeemember

• Pravosudov, Vladimir
• Logan, Michael
• Riddle, Misty
• Matocq, Marjorie

• Avian Physiology
• Food Availability
• House Wren
• Maternal Hormone Transfer
• Urban Ecology
• Wildlife Behavior

Repository record dc:identifier.uri

https://scholarwolf.unr.edu/handle/11714/10973

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/10973