The effects of anthropogenic noise on nest defense behaviors in eastern bluebirds (Sialia sialis)

Abstract

Behavior is an important way to determine how different ecological circumstances such as urbanization, pollution, deforestation, etc., can affect an individual. Individual personality behaviors can affect fitness by constraining behavioral plasticity, which may affect an individual’s response to a sudden environmental change. Studies have shown that anthropogenic noise, or the noise produced by humans, can affect learning capabilities, reproduction, and levels of aggression. However, few studies have examined how anthropogenic noise affects personality behaviors. This study examined how anthropogenic noise due to urbanization can affect eastern bluebirds (Sialia sialis) in terms of their levels of aggression. The goal of this study was to provide support for the hypothesis that, with increasing anthropogenic noise, bluebird aggression would increase as well. We used both simulated territorial intrusions (STI) and human territorial intrusions (HTI) for obtaining this aggression data and tested whether or not HTI trials could serve as a replacement for STI trials. We also examined if body condition was affected by anthropogenic noise. We found no correlation between levels of anthropogenic noise and aggression, but female body condition was found to be negatively correlated to low disturbance frequencies. This diminished body condition could result in less energy available for aggression, possibly explaining why no relationship between anthropogenic noise and aggression was found. We also found that the HTI elicited different responses than the STI and concluded that it could not serve as a substitute.