Anthropogenic changes disrupt animals’ abilities to carry out functions necessary for survival and reproduction. One such recognized disturbance is the disruption of animal vocalizations by anthropogenic noise and acoustic masking; however, there is need to examine the effects of these disruptions on communication and relating them to behavioral indicators of an altered soundscape. We examined the effects of anthropogenic noise on acoustic diversity and avian vocalization and communication. We used automated recording units to measure the soundscape and quantified the soundscape by measuring different soundscape indices. We measured frequencies of Carolina Chickadees’ (Poecile carolinensis) alarm calls, and tested if vocalization frequency differed in response to levels of anthropogenic noise and overall variation in soundscape. We observed Carolina Chickadee and Tufted Titmouse (Baeolophus bicolor) behavioral response to high and low frequency Chickadee vocalization playbacks to test the proximate functionality of possible vocalization shifts.
We found that anthropogenic noise did have measurable impacts on biophony and acoustic diversity, acoustic indicators of animal communicative behavior. However, we found that Chickadee vocalization frequency did not change in differing levels of anthropogenic noise or in differing soundscapes. From the alert response analysis, we found that vocalization frequency shifts did not provide an advantage in overcoming acoustic masking, possibly explaining the observed lack of frequency shift. Combined these data suggest that assessment of behavioral response to anthropogenic noise needs to extend beyond simple measures of vocalization frequency to include both functional response and broader community measures of behavior.