The impacts of sleep disturbance on birds: a review of the knowledge gaps

Sleep is an evolutionarily conserved behaviour critical to animal function. While the exact functions of sleep are still unclear, the ubiquity of sleep behaviour and its potential high costs (e.g. reduction in foraging time, increased vulnerability to predators) suggest sleep serves a critical role for animals. Animals that share environments with humans, such as urban birds, face numerous anthropogenic stimuli that are likely to fragment or alter their sleep. In this literature review, we synthesise the current research available on sleep disturbance in birds and provide suggestions for future research to address key gaps. Our analysis revealed that knowledge on how sleep disturbance affects birds is currently fragmented, is often inferred rather than explicitly measured, and fails to connect causal mechanisms to ecologically relevant outcomes. To address these critical knowledge gaps, we suggest that future research on sleep should: 1) incorporate both the effect of stimuli on sleep and the resulting consequences of this sleep loss on the behaviour and fitness of the study species; 2) broaden to include contexts other than migration and seasonal change; 3) include juvenile birds that are still in the development phase; and 4) explore a greater range of the potential functional consequences of disrupted sleep. Understanding the fitness‐related consequences of sleep disturbance from anthropogenic stimuli will provide critical insights into the impact of these stimuli on birds, and how to mitigate the impacts of sleep disturbance in urban environments.