Q: We have a male cardinal who keeps flying off a bush next to the house and bumping up against a nearby window.  The question is why is he doing that? Is he trying to attract a mate or just showing off? Or, seeing his own reflection in the glass? He goes through this routine for at least 15 minutes twice a day.

 This one required some research and here is what we found. It's thought that birds hit windows because they see the landscape—trees, sky, clouds—reflected on the glass surface but do not realize that a hard, transparent surface lies between them and that apparent open space. Panicking birds, fleeing for cover to escape predators, are even more likely to fly into windows.

A related problem—more annoying than lethal—occurs when birds attack windows. It usually occurs in spring, and is due to birds' urge to defend breeding territories. The male cardinal pecking at your window is likely fighting what he perceives as an intruding male—he doesn't understand that it's his own reflection. This territorial reaction may be so strong that the bird may exhaust himself, but it usually doesn't result in fatal injury.  Thanks for another great question, please keep them coming.