Birds spend a great deal of time preening and caring for their plumage, and woodpeckers are no exception. This flicker is either sunning or anting to help condition its feathers.
Sunning is one way birds condition their feathers. They spread their wings out flat on the ground, exposing individual feathers to the sun (see videos).
Anting is another way. They do this by spreading their wings out near an ant source and letting the ants crawl on their wings & body. The ants release formic acid as they move about, which kills parasites on the bird. For the flicker, the ants can then become a meal when they are through, which is a great arrangement for the bird, not so good for the ants!
Flicker has the longest tongue of the five species in this area.