Spring means bluebirds

Spring must be here. We've got a bluebird hanging around. He doesn't seem as interested in the bluebird houses, as much as just squabbling at us while we're outside. He also has been guarding the bird feeders, even though he doesn't eat from them. My husband reports that he's been flying up to the windows - mostly in rooms where the family is. The one time he didn't fuss is when my husband when down back to straighten up the bird houses. It seems this bird has an agenda for us, we just don't know what it is.