Twice a year more than 5 million birds from at least 250 different species fly through the city of Chicago alone as they head toward Canada in the spring and return south toward Central and South America in the fall. Though beautiful, the Windy City’s skyline can prove fatal to a number of birds who collide with glass-covered or illuminated buildings. 

Studies have estimated at least 100 million bird deaths related to light pollution in cities throughout the United States per year, and some estimates put that number closer to one billion deaths per year.