Date of Award
Master of Science
Dr. Scott MacDougall-Shackleton
Many songbirds use information from the environment to coordinate seasonal reproduction. American goldfinches (Carduelis tristis) demonstrate seasonal reproduction but differ from other songbird species by delaying reproduction until late- summer. Using correlational evidence collected from nesting cards across North America, I determined that timing of breeding for goldfinches was significantly related to ambient temperature and thistle blooming phenology. In a captive experiment, my results demonstrate that temperature and blooming thistle phenology significantly affect gonad recrudescence and testosterone levels. In summer temperature conditions, goldfinches exposed to blooming thistle plants had significantly higher levels of testosterone compared with birds shown a non-blooming thistle plant or no plant. Goldfinches may use blooming thistles as a predictor of abundant food availability and favourable breeding conditions which then gets them into breeding condition.
Luloff, Thomas William, "THE EFFECTS OF ENVIRONMENTAL CUES ON REPRODUCTIVE PHYSIOLOGY OF AMERICAN GOLDFINCHES (CARDUELIS TRISTIS)" (2011). Digitized Theses. 3542.