We used these meta-data to identify relevant evidence for each secondary question and describe aspects of our secondary questions that may support reviews (evidence clusters) and others that require more research (knowledge gaps). We evaluated the quantity of available evidence based on meta-data fields related to study context, population traits, light source characteristics, and outcome variables. In our map, we included all studies reporting eligible populations (birds), interventions/exposures (artificial light), and outcomes (movement through space, behaviour preceding movement, or distribution). We searched multidisciplinary citation indices as well as databases and websites specific to conservation, pest management, transportation, and energy. Using the principles of systematic reviews and methods published in an earlier protocol, we conducted an extensive and interdisciplinary literature search.

We identify and describe the evidence available for four secondary questions relevant to conservation or management: aggregation/mortality at structures with artificial lights, evidence that light attracts and/or disorients birds, light-based deterrent efficacy, and the influence of continuous illumination on habitat selection. Our systematic map provides a comprehensive, searchable database of evidence of the effects of artificial light on bird movement and distribution, increasing both the quantity and diversity of studies that are accessible for further comparison and synthesis. Studies documenting aggregation, deterrence, and habitat selection are typically considered separate literature bodies, but they actually study a common set of populations, interventions/exposures, and responses. Artificial light can also change birds’ perceptions of habitat quality, resulting in selection or avoidance of illuminated areas.

In other contexts, birds are repelled by light-based deterrents, including lasers and spotlights. Birds flying at night are known to aggregate around artificial light and collide with illuminated objects, which may result from attraction and/or disorientation. Artificial light is ubiquitous in the built environment with many known or suspected impacts on birds.

Download lights out for bird migration