Urbanization introduces a set of novel stressors for animals in these modified habitats. Developing young, in particular, can be at risk due to increased predation, exposure, and high food intake requirements. Song sparrows (Melospiza melodia) are a model wild songbird system that persist in both urban and rural habitats, and have young that develop very quickly. I investigated how urbanization changes the arthropod community, how that in turn affects nestling diet, and ultimately if there were any differences in nestling amino acid profiles or body condition between habitat types. Prior work found that urban habitats also have far higher rates of brood parasitism, which can additionally restrict food intake for urban nestlings. However, this prior work has also found that urban song sparrow adults avoid consequences for living in urban habitats, so I wanted to see if nestlings were also able to avoid the consequences of urban living. In chapter one, I found our urban arthropod communities had lower average arthropod abundance, biomass, and diversity when compared to rural arthropod communities. Song sparrow nestling diets differed somewhat in composition of arthropod prey items by habitat, but urban and rural nestlings had the same average biomass of stomach contents. In chapter two, I investigated whether different habitat types or brood parasitism altered body size and amino acid concentration of song sparrow nestlings. Only gamma-aminobutyric acid differed, being significantly lower in urban, parasitized nestlings. No groups differed in metrics of body condition. In chapter three, I performed a meta-analysis to investigate how brood-parasitic brown-headed cowbirds (Molothrus ater) affect host clutch size and nest success. Host clutch sizes were lower when parasitized, but surprisingly non-parasitized nests were more likely to fail. Despite lower arthropod food availability and high levels of brood parasitism, urban song sparrow nestlings are not compromised, supporting the conclusion that urbanization does not necessarily have negative consequences for individuals of this species. / Doctor of Philosophy / Urbanization introduces a set of new challenges for animals. Young animals, in particular, can be at risk due to increased predation, exposure, and lack of food. Song sparrows (Melospiza melodia) are a model wild songbird system that persist in both urban and rural habitats, and have young that develop very quickly and rely on parents providing a diet of arthropods, including spiders and insects. I investigated how urbanization changes the arthropod community, how that in turn affects nestling diet, and ultimately if there were any differences in nutrition or body condition. Urban habitats also have higher rates of cowbirds laying their eggs in the nests of other species, which can make it even harder for urban song sparrow nestlings to get enough food. However, this prior work has also found that urban song sparrow adults avoid consequences for living in urban habitats, so I wanted to see if nestlings were also able to avoid the consequences of urban living. In chapter one I found our urban arthropod communities had lower average number and mass of arthropods, when compared to rural arthropod communities. Song sparrow nestling diets differed somewhat in composition of arthropod prey items by habitat, but urban and rural nestlings had the same average biomass of stomach contents. In chapter two, I investigated whether different habitat types or having cowbird 'siblings' resulted in different nutrition and body size of song sparrow nestlings. Out of nearly 30 measures of nutrition only one differed, being significantly lower in urban nestlings with siblings. No groups differed in body size. For chapter three I analyzed the literature to investigate how brown-headed cowbirds (Molothrus ater) affect the number of eggs host birds lay and host nest success. Host clutch sizes were lower when cowbirds were present, but surprisingly, it was nests without cowbirds that were more likely to fail. Despite lower arthropod food availability and high levels of cowbird presence, urban song sparrow nestlings avoided negative consequences, supporting the conclusion that urbanization does not necessarily harm individuals of this species.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/120991 |
| Date | 22 August 2024 |
| Creators | VanDiest, Isaac |
| Contributors | Biological Sciences, Sewall, Kendra, Hopkins, William A., Gilbert, Elizabeth Ruth, Belden, Lisa Kay |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | Creative Commons Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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