Date of Final Oral Examination (Defense)
Type of Culminating Activity
Master of Science in Biology
Jesse R. Barber, Ph.D.
Julie Heath, Ph.D.
Ian Robertson, Ph.D.
Natural sounds are an often overlooked, yet important component of an animal’s habitat. The acoustic environment may be especially significant during foraging, because a noisy world can limit auditory surveillance. Here, we investigated how natural noise structures the foraging vigilance trade-off to understand how intense acoustic environments may have shaped antipredator behavior across the evolutionary past, and better inform conservation efforts in the present.
First, in Chapter 1, I directly compared the foraging and vigilance behaviors of captive song sparrows (Melospiza melodia) in anthropogenic and natural noise. We recorded foraging trials in 4 playback conditions (roadway traffic, whitewater rivers, whitewater rivers shifted upwards in spectrum, and amplitude-modulated rivers), along with an ambient control to assess which acoustic characteristics make a foraging habitat risky. We found that sparrows increased vigilance or decreased foraging in 4 of 6 behaviors when foraging in higher sound levels, regardless of playback type, indicating a broad role for noise in antipredator behavior.
Next, in Chapter 2, I sought to understand the ecological relevance of these findings by examining wild bird behavior. To do so, we broadcast the same whitewater river noise as used in our lab experiment across a riparian landscape. To understand if the spectra of the acoustic environment affected bird behavior, we also presented spectrally-shifted whitewater noise to produce a gradient of frequencies. Using 18 bird feeders placed across this landscape, we recorded and analyzed behavior of the three most common bird species. Black-headed grosbeaks (Pheucticus melanocephalus) and lazuli buntings (Passerina amoena) demonstrated an increase in at least one vigilance behavior in high sound levels, while American goldfinches (Spinus tristis) and grosbeaks altered some behaviors according to background frequency. Clearly, adjusting antipredator behavior in noise is conserved across diverse bird species.
Taken together, our findings imply that natural soundscapes have likely shaped behavior long before anthropogenic noise, and that high sound levels negatively affect the foraging vigilance trade-off in both anthropogenic and naturally intense acoustic environments. These results are concerning in light of ever-increasing anthropogenic noise pollution.
Sweet, Kate Antonia, "Natural Noise Can Influence Bird Foraging and Vigilance Behavior" (2021). Boise State University Theses and Dissertations. 1795.
Available for download on Monday, May 01, 2023