Electronic Thesis and Dissertation Repository


Master of Science




Dr. Chris G. Guglielmo


In passerines, the endocrine modulators responsible for seasonal changes in migratory behaviour and physiology are unclear. Spring photoperiods alter androgen levels, influencing muscle mass and fat deposition rates to power migration, as well as enhance nocturnal migratory restlessness activity (Zugunruhe). My study compared physiological indicators and migratory restlessness in castrated and intact white-throated sparrows (Zonotrichia albicollis) following photoperiod and hormone manipulation. Nocturnal restlessness activity was highest in migratory intact males or migratory castrated males that received testosterone replacement. Liver mass decreased in all photostimulated migratory groups regardless of testosterone treatment. Likewise, oxidative enzyme activity was unrelated to testosterone, but was higher in the migratory males relative to the non-migratory group. My results indicate that long day photoperiods in spring will enhance nocturnal restlessness through testosterone, but that testosterone does not appear to be responsible for changes in oxidative enzymes or digestive organ mass.