Downy woodpecker (Picoides pubescens).
Male downy woodpeckers have a red nape. Females do not.
Downy woodpeckers like both sunflower seeds and suet. Also insects. They have long barbed tongues for pulling insects out of small places, according to Birds of New Jersey.
The challenge with downy woodpeckers is to distinguish them from the larger hairy woodpecker. The downy has a shorter, thinner bill, as seen in the photo above, and small black spots on the side of the tail, as seen below, which are sometimes hard to see.
They have stiff tail feathers, which help them balance in all the acrobatic positions they get into.