As long as people have been putting using glass in buildings, birds have been smacking into it. Sometimes the buildings are too tall, or in a centuries-old flight path, and sometimes the birds are just … well… bird-brained.
This art school in Chicago put stickers of birds on its windows to maybe give the birds a clue that the wild blue yonder doesn’t continue through the glass. I’m not an expert on birds, but I wonder if the silhouettes chosen are predatory birds, meant to scare other birds away. They kind of look like owls to me.