SONG AS AN AGGRESSIVE SIGNAL IN THE BACHMAN'S SPARROW

We conducted a field experiment to study the male-male aggressive function of song and singing behavior in the Bachman’s sparrow (Peucaea aestivalis). An aggressive signal is one that is 1) associated with an aggressive context, 2) predicts attack or escalation towards attack, and 3) is responded to by receivers appropriately, i.e., with aggressive escalation or retreat. We are testing these predictions for three categories of Bachaman’s song ‘primary song,’ low amplitude ‘whisper song,’ and ‘excited song’ produced by territorial males in response to a threat by a rival male. In May-July 2016 we performed simulated territorial intrusions (STIs) on the territories of 30 male Bachmann’s sparrows at Johnathan Dickinson State Park. We are quantifying subject males’ vocal and other behavioral responses with the aim of determining which vocal behaviors, if any, are reliable threat signals and if particular sequences of signals predict escalation versus de- escalation. To do this we will determine the frequencies of each song category and aspects of singing behavior (song rate, song type switching rate) and will relate these signaling behaviors to aggression using linear regression and discriminant function analyses. In addition, we are analyzing movement, proximity, and attack behaviors to quantify each male’s aggressiveness. Our results will contribute to a better understanding of the social behavior and communication system of this species.