Why is a little bird tapping on a Los Gatos window?

DEAR JOAN: I live in the foothills and for the past two weeks, every morning between 7 and 7:30, a little bird lands on the frame of an upper window in our bedroom and proceeds to peck vigorously several times at the window, turns away a couple of seconds, sometimes hops to another spot, then repeats this cycle a few times, then flies off, often returning after a while, and then quits for the day.

What bird is this, and what is this strange behavior?  Is it attacking its reflection? If so, why, and doesn’t a bird learn after a while?