Meeting Abstract
Striking tradeoffs between survival and reproduction is essential to maximizing fitness. Because individuals in many taxa rely on territories for resources and mating opportunities, territorial defense is often a vital component of reproduction. However, territorial displays can be costly as they may decrease survival by increasing visibility to predators. Territorial aggression is therefore expected to be plastic, but the degree to which individuals alter their behavior may vary. This study investigated if life history factors explain variation in plasticity and asked whether plasticity is correlated with fitness by conducting simulated territorial intrusions (STIs) on male Dark-eyed Juncos (Junco hyemalis). Each individual (n=26) experienced two STI treatments in randomized order: a high-risk treatment using an Eastern Screech-Owl mount and a low-risk using a novel object. The difference in response was measured as plasticity. Overall, the presence of the owl significantly decreased aggression, especially mean distance and latency to closest approach. As anticipated, plasticity varied immensely among individuals, and a multivariate linear model revealed several non-significant trends. Older males tended to be more plastic, potentially because this trait enhanced their survival at a younger age. Males in better condition tended to be less plastic, possibly because stronger flight muscles allow them to better escape from potential predators. Plasticity did not correlate with breeding success or recapture the following year. These data suggest that territorial plasticity is not under selective pressure, but may confer differential advantages to individuals based on life history traits such as age and condition.
