A billion birds killed yearly by US skyscrapers - study

A new study estimates that as many as a billion birds die each year in the US when they collide with buildings, especially glass-covered or lit-up skyscrapers. Chicago was found to be the most dangerous city for birds, with the busiest avian airspace during migration combined with a high number of glass buildings. Kyle Horton is an author of the study from the Cornell Lab of Ornithology.