Red cardinal hanging around for two days pecking at car side mirror?

Hey, welcome to Fluther.
I’ve seen cardinals do that with reflective windows. He probably thinks he sees another male and is trying to fight him.
Just be glad that it’s not a peacock or a vulture! They can do some serious damage to cars.

He’s being territorial (and not that bright), thinking his reflection is a rival male.

Mating season brings out some odd territorial behavior.

Here is a good article on How to stop birds from pecking at mirrors

I spray a little WD-40 into the housing behind the mirror. That lubricates it while discouraging critters. I short squirt and you’re done.

It also keeps yellow jackets, wasps and spiders away.

Everyone else got it. I just wanted to chime in to add that it’s a good idea to be proactive about keeping the birds from doing this or they’ll eventually start sitting on the mirrors and get poo all over them. Also, welcome to Fluther!

Yes, he is seeing his reflection as another bird. This is also why many small caged birds are given mirrors in their cages to simulate a companion. I have pet geese and they will do this with the shiney chrome bumpers on cars or vehicles which reflect their image. Animals are not self aware enough to discern their reflection as being themselves.
Breeding season is right around the corner for songbrids and many other species, beginning in Feb. and in full swing by March/April through July. The Cardinal is feeling his birdie testosterone.

Probably has a nest nearby, hence the territorial behavior.

@Mariah Songbirds are not nesting now, it is not quite breeding season yet, and they do not live in nests year round, nest building is only in the spring for raising baby birds. In winter birds flock up and stay nomadic seeking food in flocks for maximum survival success. :-)

My MIL has this problem every year. She just puts some plastic grocery bags over them with rubber bands so they can be taken off quickly and effortlessly.

@Coloma Ooh okay, thanks for the correction.