A Carolina wren must have a nest nearby.  I have seen it repeatedly hop on the posts of our fence and sing out from my front door.  It has a beautiful voice I was not familiar with it (???).  As far as wrens go it is big.  Now I am looking out for it and trying to discover its nest which is probably in the adjacent gigantic bush.  Catbirds have nested there before.  Last year a Carolina wren had a nest in a flower pot hanging from the garage door.  Carolina wrens are birds I have fallen in love with.  It was one I was unfamiliar with until I started putting up bird feeders.