Backyard Wintertime Nature in New Jersey.
Other than some tiny birds that can get into this bird feeder, the Red-bellied Woodpecker has a long enough beak to reach the sunflower seeds. It then has to take the sunflower seed to a tree to break it open. I seems that only the Cardinals and Finches can open sunflower seeds directly in their beak.
Individual images in the slide show can be viewed here.