An ecoacoustic approach to understand the effects of human sound on soundscapes and avian communication

Abstract

ABSTRACT Anthropogenic sound disrupts animal communication, but little research has both quantified how this disruption changes the soundscape and connected these changes to shifts in avian behaviour. We examined the effects of anthropogenic sound on soundscapes and avian vocalisation and flight behaviour. We recorded Carolina Chickadee (Poecile carolinensis) vocalisations, tested if vocalisations differed with varying levels of anthropogenic sound and overall variation in soundscape, and observed behavioural responses to differing vocalisation playbacks to test the functionality of possible vocalisation shifts. We found that anthropogenic sound disturbance predicted change in soundscape indicators. Vocalisation frequency was higher in areas of high disturbance but did not differ with changes in soundscape. Vocalisation frequency shifts did not provide a functional advantage, possibly explaining the lack of vocalisation changes in response to disturbed soundscapes. These analyses demonstrate that anthropogenic sound does change the surrounding soundscape, but the interaction between these changes and animal behaviour is multidimensional. Key policy insights By quantifying the effects of sound from roads on the surrounding soundscape, we demonstrated how anthropogenic sound disturbance impacts the surrounding ecosystem, not just the immediate site of the generated sound. Increasing anthropogenic sound disturbance affected avian vocalisation. Birds vocalised at a higher frequency in the presence of higher anthropogenic sound disturbance. Vocalisation frequency shifts did not provide an advantage in overcoming acoustic masking from roads. The assessment of vocal responses to anthropogenic sound needs to extend to include complex assessments of behaviours. Without these behavioural assessments we may not be able to properly evaluate the effects of anthropogenic sound disturbances on avian communication and behaviour.