When Birds Collide, With Buildings - City Room Blog - NYTimes.com By By Jennifer 8. Lee
Dr. Klem estimated in a 1991 study that between 100 million and a billion birds die each year in glass collisions — that’s a huge spread, we’d like to point out — which would make the single greatest human-caused reason for bird deaths in the United States [pdf]. He said that his research since then shows that the one billion figure is conservative.
And it’s not only the architecturally tall buildings that cause problems. Rather, the most hazardous areas of all buildings are the ground level and bottom few stories — in part because those reflect the surrounding tree canopies. So birds can hit even short, squat buildings.