Behaviour 2019
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Daily Behavioral Activity Patterns and Testosterone Levels in Captive Dark-Eyed Juncos
Emily K Elderbrock, Emily A Porter, Timothy J Greives. North Dakota State University, Fargo, ND, United States

Individuals exhibit variation in daily activity patterns which may impact their reproductive success. Sex steroids influence endogenous timekeepers in lab animals and as such may be important regulators of activity rhythms during the reproductive season in wild animals. However, it remains unclear whether natural variation in sex steroids influences individual variation in daily timing of behaviors. In this study, we investigated the relationship between testosterone levels and daily activity rhythms in captive male dark-eyed juncos. After a month housed on a short-day photoperiod, we photo-stimulated individuals and determined peak testosterone levels with an injection of gonadotrophin-releasing hormone (GnRH). The birds responded to the GnRH injection by increasing testosterone, indicating that they were in reproductive condition, however during this same period, birds displayed high levels of nighttime activity. We found no relationship between testosterone and onset of activity during short days. We were unable to clearly assess onset of activity during long-days and further analyzed our data for individual flexibility in response to light cues and timing of migratory behavior.