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Author ORCID Identifier


Open Access Dissertation

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Organismic and Evolutionary Biology

Year Degree Awarded


Month Degree Awarded


First Advisor

Alexander R. Gerson

Subject Categories

Biology | Comparative and Evolutionary Physiology | Ecology and Evolutionary Biology


Animal life has evolved innumerable strategies to adapt to a great range of environmental conditions present on earth. The physiology of free-living animals has thus been shaped to allow for maximal performance under challenging conditions and has given rise to traits that enable animals to overcome daunting ecological pressures. Few life history stages in the animal kingdom rival the intensity of annual avian migration: the extreme metabolic requirements of long-distance flight coupled with navigating vast and hostile ecological barriers results in enormously high mortality for young birds. It is therefore the main focus of this thesis to identify physiological traits which are important in assisting successful songbird migration. In the subsequent chapters, I focus analysis on the interplay between body composition, metabolism, and whole-animal performance in ecologically-relevant contexts.

I investigated (1) how reduced body condition incurred during flight constrains whole-animal performance and the ways that birds compensate physiologically and (2) the relationship between lean body mass and metabolism, and its implications for interpreting the metabolic requirements of songbirds. The innovations in my methods are largely due to the use of an emerging technology, quantitative magnetic resonance (QMR), allowing for the rapid quantification of body composition in free-living animals. Furthermore, I’ve employed the use of high-throughput multiplexing for measuring metabolic rates, which has allowed me to compile a substantial dataset on the metabolism of migratory songbirds.

I present empirical evidence which provides key insights for how birds cope with the challenges of migration. In the chapter II, I demonstrate that songbirds can rapidly modulate digestive enzymes during refueling to assist in replenishing lean tissue mass. Chapter III investigates the relationship between body composition, metabolic rates, and real-world refueling performance at stopover. My final chapter focuses on the interpretation of the basal metabolic requirements of songbirds, specifically how organismal size and evolutionary history may govern both intra- and interspecific variation in metabolism.


Creative Commons License

Creative Commons Attribution-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-No Derivative Works 4.0 License.