If you have not made it to a bird blind, I suggest you do it during the winter as the birds are hungry and not quite as camera shy. This red-headed woodpecker was definitely trying to control one of the feeders. If another bird approached the feeder, this one would sound a raucous "kwrrk" and force the other bird to flee.
In the area, there are two public bird blinds, on at Wickiup Hill Learning Center, Linn county and the U of Iowa Macbride Field Campus north of North Liberty. Both have their unique features and "clients".