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Full-Text Articles in Life Sciences
The Effect Of Testosterone On The Spring Migratory Phenotype Of A North American Songbird (Zonotrichia Albicollis), Caitlin L. Vandermeer
The Effect Of Testosterone On The Spring Migratory Phenotype Of A North American Songbird (Zonotrichia Albicollis), Caitlin L. Vandermeer
Electronic Thesis and Dissertation Repository
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, …
Tundra Swan (Cygnus Columbianus Columbianus) Habitat Selection During The Nonbreeding Period, Katelyn H. A. Weaver
Tundra Swan (Cygnus Columbianus Columbianus) Habitat Selection During The Nonbreeding Period, Katelyn H. A. Weaver
Electronic Thesis and Dissertation Repository
Changes in availability and foraging profitability of agricultural and aquatic habitats have the potential to greatly influence population dynamics of waterfowl. Therefore, the purpose of my research was to understand habitat selection by Tundra Swans during the nonbreeding period and to explore the scale-dependency of these relationships. Habitat selection was influenced by seasonal changes in nutritional requirements and food availability; Tundra Swans selected open water and agriculture in winter, wetlands were weakly selected during migration when open water was strongly selected (especially during autumn), and there was a 2-fold increase in use of agriculture from autumn to spring. It appears …