I guess this isn't the typical White-breasted Nuthatch pose, but I kind of liked this shot. Eat looked to be eating bark or something in the bark. This bird was not attracted with seed of any kind.
Ryan I agree about this being an unusual pose. You got nice head angle and the eyes seem to be sharp. It's a little too tight in the frame for my liking though. I would also suggest burning the OOF light blur in the LR corner of the frame. My eye seems to be drawn to it as presented here.
I like the idea and the piece of wood in its beak adds to it. I don't mind the tight crop but find the branch at the bottom a bit too prominent. I might tone down the whites some.