My problem was a Cardinal who did that every day. I read that when a Cardinal comes to visit, it means a friend or family member, who has passed ,is close-by. After that I would always say "hello Diane" to a dear friend who died suddenly and I miss so much. After I said it the bird left and has not been back to attack my windows but still comes to my yard when I'm out there. I should add that I've been at this location for 30 years and perhaps saw 3 Cardinal's in all that time. I now see him/her, there are a pair of them, every day.
I also lost a nephew this Spring and he loved Bluebirds. Bluebirds have made a home in one of my birdhouse so I can watch them from close-by. I feel Kevin sent them to me to bring me happiness.