Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

Climate change threatens animals of all taxa across the globe and young birds are particularly susceptible to environmental changes while developing in the nest. Environmental changes including shifts in temperature, rainfall, and humidity can affect developing nestlings in numerous ways, including disrupting incubation patterns and increasing nestling exposure to ectoparasites. In my dissertation, I sought to study possible effects of increased temperature, decreased humidity, and increased ectoparasite exposure on the physiology, growth, and development of wild nestling European starlings (Sturnus vulgaris) across two years in the field. In the first study, I experimentally increased temperature in the nest as eggs were laid to increase asynchronous hatching and studied the effects of hatching asynchrony on the last-hatched nestling (runt) in each nest. I found that runts from nests where eggs hatched over multiple days were significantly less likely to survive and stayed smaller than runts from nests where eggs hatched synchronously (all on the same day), but otherwise, suffered limited physiological impairment. These results suggest that increased asynchrony due to climate change could reduce the survival of altricial songbirds, especially for runts in a clutch. In the second study, I experimentally reduced humidity in the nest to study how changes in humidity affect ectoparasite abundance, while also adding mites to a subset of nests to study the effects of increased mite exposure on nestling growth and development. While the effects on humidity were subtle, our mite treatment successfully increased mite load. However, I found no effects of increased mites on nestling survival, growth, or physiology, suggesting that nestlings are resilient to low numbers of mites. For the third study, I swabbed nestling skin across two field seasons and scored ectoparasite abundance to measure the effects of ectoparasites on the development of the nestling skin microbiome, which has been linked to fitness-related traits such as immunity and growth. Across both years, I found that mites resulted in a decrease over time in at least one index of alpha diversity of the nestling skin microbiome. Mite treatment in year 2 also affected beta diversity of the nestling skin microbiome and the relative abundance of several bacterial taxa. These results demonstrate that ectoparasites can impact the development of the nestling skin microbiome and may cause deleterious effects if these changes persist into adulthood. Together, the three chapters of illuminate the effects of environmental challenges nestlings face in a changing world.

Date

7-20-2024

Committee Chair

Christine Lattin

DOI

https://doi.org/10.31390/gradschool_dissertations.6531

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Available for download on Tuesday, July 13, 2027

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