It sounds like you know about cardinals. I have a beautiful, but neurotic one in my yard. It attacks the mirrors, windshield and windows of our vehicles...and starts hitting our kitchen window a little past sun up. It is a beautiful bird, BUT my side mirror is badly scratched, and my kitchen window is 'etched' from the repeated hits (at just about the same spot...like it is a 'bullseye.' I have tried putting black paper up on the inside of the window in question, along with hanging a windsock (with long kitelike tail) hoping that the movement would distract the bird...but it still keeps hitting the cars and window. This started back in September...any suggestions?
My mom has a chickadee that raps on the window when the feeder gets empty. Fortunately they are tiny and don't do much damage.
You might try putting up one of those plastic mirrors they sell for pet birds at his favorite spot.
Cardinals are pretty territorial. Maybe he's just practicing his sparring techniques!
:)
Oh my goodness, sounds like you have a Cardinal with "issues" on your hands. LOL! Perhaps he's lonely. Does he appear to have a mate?