Two dead birds and a building in polarized light

Robertson lab: polarized light and bird-building collisions

Migratory birds facing a number of hazards during their journeys. Collisions with buildings have become a major conservation problem for them, but the exact reason why so many birds collide with buildings is unclear. Several studies suggest that birds are attracted to nighttime building lighting. Bruce Robertson helped discover a new kind of light pollution, polarized light pollution, that could also be responsible. The light that reflects from glass buildings gets polarized, which may cause it to look like a water body at a distance, instead of a large dangerous object approaching fast. This collaboration between Bruce Robertson at Bard College and Sirena Lao and Scott Loss at the University of Oklahoma asked whether polarized, or unpolarized light pollution was more strongly associated with bird collisions with buildings in downtown Minneapolis. We found that birds were most likely to collide with individual windows that were lit at night, but that there was little evidence that polarized light pollution was attracting birds. This suggests that turning out the lights in each room of office buildings can help migratory birds avoid collisions.

Lao, S., Robertson, B.A., Anderson, A.W., Blair, R.B., Eckles, J.W., Turner, R.J. and Loss, S.R., 2020. The influence of artificial night at night and polarized light on bird-building collisions. Biological Conservation, 241, p.108358.