Knock knock. Who's there?

I've been working in my office this morning (it used to be a porch) and keep hearing an occasional knock on the door, which at first I thought must be snow falling off the roof. When curiosity got the better of me and I finally peered out, I discovered this fellow, nestled up against the door on the deck, tucked out of the wind, cleaning up the birdfeeder fallout.

Several hours later: Now I am a bit worried about this rabbit.  Before tackling chores I went out with my camera, and the rabbit was still on the back steps.  I was able to get pretty close, and he didn't flinch, despite the fact that when I turned around, Cocoa was standing right behind me. She was oblivious to the rabbit, though, and I walked away calmly and she followed.
He's still there!