I'm wondering.  He sits atop the tower and sings all morning.  I never see a Mrs. cardinal.  I wonder if he's hoping to attract one.  Makes me feel rather bad if he's lost his mate and keeps hoping that she will show up.

This is what we used to see  http://www.angelfire.com/realm2/ancient0/images/cardinals.SWF  it's him feeding either his spouse or a young one.  Note if you have a pop up blocker it will probably block the angelfire ad but if you don't there will probably be an ad or two.

It takes a minute into the video to see him feeding the other.