Research by ornithologist Daniel Klem Jr. of Muhlenberg College indicates that as many as one billion birds die each year in the United States due to collisions with windows.

Daniel Klem's research also examined various methods of preventing the collisions. He found that by placing visual clues such as window decals on the window at no more than 5cm-10cm apart, the birds could be effectively deterred from flying into the glass.

Find out more:

• Collisions Between Birds and Windows: Mortality and Prevention (PDF) (Journal of Field Ornithology)
• Windows: A Clear Danger to Birds (NPR)
• Clear & Present Danger (National Audubon Society)
• A Billion Birds Die in Plate Glass Plate (Wildlife Protection)
• Human Causes of Bird Fatalities (Curry & Kerlinger)

What you can do:

• Reduce Bird Collisions on Windows (Whispering Windows)
• Protecting Windows From Flying Birds (RLRouse)
• Minimizing Window Collisions (National Audubon Society)
• Birds and Windows (RSPB)
• Feather Guard (FeatherGuard.com)

Photo © Feng Yu