The Downy and Hairy Woodpeckers are strikingly similar. Three main differences are the size of the beak, overall bird size, and tail feathers. The Hairy has a long beak, the Downy a short beak. The Hairy is about 9-1/2" in length compared to the Downy's 6-1/2" length. The Downy's white tail feathers are marked with black bars; the Hairy's is pure white. Looking at this particular bird, the beak appears quite long in proportion to his face, making me think it's a Hairy. But I'm noticing black bars on the tail feathers. Ugh. Unless the two are side-by-side, it's really difficult to tell these cousins apart. Thus the question mark.
400mm | f/7.1 | ISO 640 | 1/400 sec