Backyard visitor

This visitor showed up last week just outside my back door. (That's a porch-roof support the nest is sitting on.) The first few days she took off as soon as I opened the door to enter or leave, no matter how gentle I was about it, but since Sunday my comings and goings have not disturbed her. I assume there are eggs and that protecting them is more important than fleeing me.

nest from below, dark head visible

I took that picture this morning and the colors are true (no adjustments), though it was in shade. I took the following one this evening and adjusted for longer exposure because it was in shadows (but this one shows more of the body):

nest from other side, head and tail visible

I estimate the bird to be about 8" from beak to tail. I've never seen the wings or belly clearly (just the blur of hasty retreat those first few days).

What kind of bird is this? I looked up some sites that list common western-PA birds and, among the pictures I found there, this seems closest to the downy woodpecker. But it doesn't seem especially downy, and those white rings around the eyes don't match any pictures I found. Some woodpeckers have white stripes, so maybe this is just a variation. The beak looks about right for some sort of woodpecker, as opposed to the smaller beaks on some other birds.