Woodpeckers generally are a great study for the budding bird photographer. Rotted wood attracts especially the larger foraging birds, and nests are relatively easy to find. Some woodpeckers are fairly tame, especially in-city. Others are skittish. I’ve found the Lewis’s Woodpecker particularly difficult, even with a blind. If you find you’re changing the bird’s behavior, back off and look for other opportunities.
Update 6/12/2020: larger images, and half-dozen new ones.