My busy cardinal

A male cardinal has been attacking our windows for about a month now.  It happened last year, too but I was able to stop it within a week or so (I hung paper towels on the outside of the windows to cover his reflection, which I thought was what he was attacking).  This year, that didn't work.  Neither did putting up lines of string (he attacks the string).  I finally got those decals of hawks but he's attacking them now!

I believe he thinks it is his job to "protect" his wife and babies from intruders.  He's doing a great job!

Believe it or not, he gets worse when the cats are sitting on the windowsills, watching him.  The bird and the cats "attack" one another through the windows.  The cats think this is the greatest toy I ever bought them!

I am hoping he doesn't hurt himself and eventually wears himself out.  Right now, he starts at around 8, hits the windows every few seconds until around noon.  Then he takes a break until 2 and goes until 5.  He attacks five different windows on three sides of the house and alternates them.  First the dining room bay window, then the laundry room, then the living room, then the dining room back window, and so on ...  Sometimes he'll hit the kitchen window but it is not always included in the cycle.

It may have something to do with the way the sun hits the windows but I haven't been able to figure it out yet.

Any ideas?

He can see his reflection in the window, thinks it's another bird and is protecting his family from it..

This is some info I found on a birdlife protection site:

Can They Harm Themselves?
Despite the violent appearance of this behavior, from the other side of the window, the birds very rarely kill themselves, all though there could be injury to the bird's beak if the behavior continues.

How Long Does the Behavior Last?
The breeding season, the time in which birds mate, build nests, lay eggs, and raise young, is the time when birds are most territorial. For robins and cardinals, the breeding season may total seven or eight weeks; and the "window fighting" may continue off and on between April and August as two or three broods are produced during that time. Quite often the behavior stops during the month of May, possibly because the bird has chosen a new nesting territory.

SITUATIONS AND SOLUTIONS

Window Attacks
Reason would suggest that covering reflective surfaces would eliminate the behavior, but this is not always the case. When the outside of the glass is covered, the bird may go searching for its imaginary rival at other windows. Not surprisingly, it will find the intruder at every window it encounters. There are reports of robins attacking as many as fifteen windows on both the first and second stories of homes. For this reason, it is probably best to be patient and do nothing. If bedroom windows are being attacked and the occupants are being awakened at dawn, cover just those windows.

If people chose to cover the windows, it is the outside that must be completely covered. A medium-weight, plastic painter's drop cloth, available at hardware stores and home centers, works well. The plastic is clear enough to allow light into the room, but cloudy enough to eliminate reflections. Attach the plastic to the top of the outside of the window and allow it to hang freely over the window. The bird will no longer be able to see itself in the window, and the movement of the plastic, as it blows in the wind, should frighten it.

Do not waste money on fake owls or rubber snakes, which reportedly frighten birds. The rival bird will still be visible in the window, and the territorial birds quickly learn that these artificial critters pose no threat.

Yes, Mani, he is seeing his reflection and thinks it belongs to an intruder. He's amazingly focused - as I said, even the cats don't scare him off. I will try the plastic and try to give the poor guy a break. Thanks for the info!

Birds can be so focused... it astounds me sometimes how the instinctive behaviour is just so entrenched!

Good luck!