I have spent many years trying to figure out a method in trying to stop birds from flying in my windows. We have many really large windows and I have tried countless ways in hoping that I could prevent this type of tragedy.
The one idea that works the best for me so far is sticking those little glow in the dark stars. What I do is put them on different spots on the window outside, the birds see them and when we look out the window we have a hard time seeing them therefore they don't obscure our view.
It is rare now that a bird hits my windows. I used to have at least over 5 birds hit the windows every day. When we shut the lights off at night the stars glow.