A Rock Wren is a bird of the arid American West. It is so adapted for the desert that it never drinks water, getting all of the moisture it needs from food.
So what was it doing in on the coast of Maine in November?
Like so many other western rarities that I have shown up over the last few months, it is a mystery. My theory is La Niña has changed the weather patterns in the west and birds are getting caught up in the jet stream and dropped into Maine.