Male songbirds use a variety of specialized singing behaviors when they interact. These behaviors are presumed to function as signals in male-male competition, yet for many behaviors it remains unclear what information the display is signaling. Examining how male birds perceive and respond to these behaviors is key to understanding how song functions in this context. Song perception by male birds is usually tested by measuring aggressive responses to song playback. The results of such tests are difficult to interpret, because the strongest aggressive response may be given to either the most threatening stimuli or to the least threatening stimuli. This project will use the cardiac response (change in heart rate) evoked by song playback as an alternative measure of the perception of song and other stimuli by male song sparrows. Specifically, this measure will be used to test the perception of low-amplitude song ('soft song'), a singing behavior that is thought to be highly aggressive, and to determine the distance over which soft song can be perceived by birds on their territories. Cardiac measures have proven useful for examining signal perception in a variety of species and contexts, but have not been applied to hypotheses about aggressive signal perception in birds.
Broader Impacts: The broader impacts of this project include promoting the professional development of women in science, and providing opportunities for undergraduate students to gain research skills and experience. Numerous undergraduates and graduates have been mentored in this program, many of whom have gone on to professional careers in animal behavior.
