Effects of Ambient Noise on Nestling Birds.

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Ambient or background noise is a universal challenge for animals that use sound to find resources, avoid predators, and communicate. Animals have adaptations to reduce interference from natural noise such as wind and rain. They are, however, increasingly exposed to human-generated noise from roadways, machinery and urban sprawl, where these adaptations may be ineffective. Human-generated noise is spreading and intensifying worldwide, and its potential to impact many animal species has been identified as an urgent conservation priority. A growing literature shows that noise can distract listeners, mask or cover-up relevant sounds, and raise stress levels, all with potential implications for reproductive success and survival. Most studies on this topic have focused on adult animals, but young animals may also be affected by noise. For instance, young of many species are especially reliant on sound to assess their environment because they are confined to burrows and nests, where vision is restricted. Also, the ability of young animals to adjust to noise is often underdeveloped compared to adults. Nonetheless, there are few in-depth studies of the effects of noise on young, free-living animals. The long-term objective of my research program has been to understand the social and environmental factors that influence parent-offspring communication in birds. Recently, the research has focused on the effects of noise on this communication system. Growing evidence suggests, however, that noise effects may extend well beyond communication and have impacts on many aspects of this early life stage. Therefore, my short-term objective is to test the hypothesis that chronically elevated noise degrades the quality of the rearing environment, with impacts on learning, stress physiology, and predation risk. In this research program, my students and I will test a) whether noise affects how nestlings learn to respond to key signals and cues from the parents, b) whether noise elevates stress hormones and c) whether the manner in which nestlings call in noise increases predation risk. In addition to these main questions, we will complete earlier work on the effects of noise on parent-offspring communication, by testing d) whether noise disrupts communication by masking relevant sounds or whether it affects communication in other ways, for instance, through distraction. This research will be the first to examine the broader effects of noise on free-living animals during early development when they may be especially vulnerable to its effects. The work will also contribute to our understanding of whether the rearing environment adaptively shapes behaviour and physiology, so that animals can better cope with changeable environments.