I have a Hairy Woodpecker with the lower mandible pushed out to the side. Its been feeding from both my sunflower seed feeder and a hummingbird feeder which I kept out long after the hummers left for the Hairy's use. See attached photos. I've also seen him pecking on a pine tree in the normal manner. The lower mandible is far enough out of the way that it can still peck at the trees without a problem, but I doubt it would be very effective in excavating any cavities.