Hormonal and Behavioral Responses to Competition: How Evolution Has Shaped Social and Seasonal Mechanisms of Aggression in a Female Songbird

摘要: Aggression is an adaptive and ubiquitous behavioral response to social competition. However, social environments often change from day-to-day or season-to-season, which can result in complex selective pressures on this key behavior and its underlying mechanisms. There is strong evidence in male vertebrates that aggression is mediated by the steroid hormone testosterone (T) over multiple timescales, but it is unclear whether and how this applies to females. In my dissertation, I tested hormonal and behavioral responses to competition over multiple timescales in female tree swallows (Tachycineta bicolor), a songbird species with a strategy of obligate, secondary cavity-nesting. Previous work revealed that aggression is beneficial for females in obtaining and defending nest sites, and that aggression is partially mediated by T, but can also interfere with parental care. In a series of experiments manipulating nest …