My first husband and I lived in a large 2 storey home with very large glass double doors across the back of the house. We always had birds flying into it, particularly after we had a reflective flim put on it to stop the sun coming in. Thsi was fine when the doors were open (there were no screens) but when they were clsoed the poor buggars would smack so hard into the glass.
I was always scared they would die of fright inside. I recall when I was a little girl, my girlfriend and I were chasing a bird around her garage trying to get it outside and it fell down stone dead after a few minutes. I felt awful about it and cried.