Birds fly into large picture windows because the glass reflects outside light, making your window appear to be clear-flying sky. Depending on how fast the bird is flying, it may be temporarily stunned . . . or killed.
Birds plowing into your windows is especially disheartening when you attract them to your home with seeds and suet in feeders. So take action to divert them away from your windows with raptor cutouts.
Yes, raptor decals are expensive, but you can make your own! Take sheets of construction paper — black works well, I also used white — and cut out the shapes of flying raptors. You can find species-correct silhouettes in most bird identification books (here you see Birds of 
Prey silhouettes from Peterson Field Guide to Birds of Western North America, by Roger Tory Peterson) or you can “wing it.” Simply cut out shapes that approximate the shape of an approaching raptor.
Put double-sided tape on the back of your cutouts, and stick them onto your window at various heights.
I attached my raptor cutouts earlier today, and no bird bombers have hit my window since. I will let you know if that changes, but I believe I have taken effective action to protect by bird friends from collision with glass that looks like sky. And, by the way, I can still look out my picture window and see the birds that visit our feeder.
P.S. We put out suet when temperatures went below zero. Some people argue against bird feeders with good logic. More on that subject in a future post. Along with the importance of providing water for your bird friends.
Critters 