Why do birds often crash into windows?

Birds do not perceive in the same way as mammals do, thus a reflection in a window may appear to be another bird. Most daytime birds have eyes on either side of their heads, giving them a large field of view but minimal depth awareness. Glass windows are worse than invisible to birds. They appear to be tempting locations to fly into by reflecting greenery or the sky. Because of the sheer quantity of windows, the toll on birds is enormous. According to a 2014 research, window strikes kill up to 1 billion birds in the United States each year.

Awnings and window screens, as well as other approaches, are occasionally used to reduce reflections and prevent birds from colliding with residences or commercial buildings. Although a bird can crash into glass at any time, the act becomes less often as breeding season approaches. What happens when birds fly into windows? Unfortunately, even when the bird is just momentarily stunned and gets to fly away, it typically dies. These birds frequently die later from internal bleeding or bruises, particularly on the head. Muhlenberg College's Daniel Klem has been researching this topic since the 1970s.