Graduation Year


Graduation Month


Document Type


Degree Name

Bachelor of Science

School or Department

Biological Sciences, Division of


Biology – Ecology and Organismal Biology

Faculty Mentor Department

Wildlife Biology

Faculty Mentor

Creagh Breuner

Faculty Reader(s)

Bret Tobalske, Tom Martin


corticosterone, life history, reproduction, avian endocrinology, stress, hormones

Subject Categories

Behavior and Ethology | Endocrinology


All vertebrates respond to stressful situations through the release of hormones called glucocorticoids (CORT). These hormones alter processes within the body to prioritize long term survival over immediate reproduction. It is hypothesized that this is helps individuals survive until conditions become more favorable for successful reproduction. Historically, stress was hypothesized to primarily to pull organisms out of reproductive life history stages when unfavorable conditions made offspring survival slim (otherwise known as the “CORT-tradeoff hypothesis”). However, recent evidence suggests that birds actively feeding nestlings show elevated CORT levels, possibly due to the increased metabolic demands of parenthood. This relationship has been named the “CORT-adaptation hypothesis”. This research tested these two conflicting associations between parental effort and stress hormones to further understand the complex relationship between stress and reproduction. During the summer of 2016 I collected blood samples to examine the levels of CORT in female tree swallows in the Seeley-Swan valley of Montana. To measure parental effort, I observed and recorded various parental behaviors including time incubating, feeding rates, and nestling growth. I compared relationships between these measurements to help explain the relationship between reproduction and CORT.

Honors College Research Project




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