Turning off building lights at night cuts bird collisions

Turning off building lights at night can save migrating birds from crashing into buildings, a study based on decades of research has shown.

Scientists found that on nights when half the windows of a large building in Chicago were darkened, there were 11 times fewer bird collisions during spring migration and six times fewer collisions during autumn migration than when all the windows were lit.

Birds use unique exploratory skills. Building lights, especially on overcast nights, can bewilder them, leading them to fly in circles. Some may crash into buildings if they recognise plants or trees reflected in the glass.