Meeting Abstract

P3-99   -   How and why female aggression varies within and among contexts: A life history perspective in the tree swallow (Tachycineta bicolor) Aguilar, EA*; Kaur, J; Rosvall, KA; Indiana University, Bloomington ; Indiana University, Bloomington ; Indiana University, Bloomington aguilare@iu.edu

Aggression is a widespread behavior expressed across many contexts, from territorial defense to antipredator protection. The degree to which this behavior is consistently displayed across contexts may be impacted by life history trade-offs, the outcome of which may vary due to condition or age. We explored these issues, focused on consistency in aggression in female tree swallows (Tachycineta bicolor). As obligate secondary cavity-nesters and single-brooded birds, tree swallows fiercely compete with conspecifics for access to a nesting territory, and they aggressively defend their eggs and chicks from predators. We used behavioral assays to measure aggression in two contexts, i.e. in the presence of a conspecific or a nest predator. We found that females were consistent in their degree of aggression within a context but not across contexts. Younger females were more aggressive towards a conspecific decoy, whereas older females were more aggressive towards the nest predator decoy. Morphological measures, including mass and wing length, did not relate to variation in aggression, but they did explain consistency in an age-dependent manner. Specifically, at least among younger females, structurally larger and heavier individuals were more behaviorally consistent. These relationships suggest that consistency changes over an individual’s lifetime or that selection may favor deviations from consistent behavior in an age-specific way. In doing so, these findings provide insight into the causes and consequences of variable degrees of behavioral consistency.