Brown Creepers are small birds that work the trunks and branches of trees in mature woods searching for insects, larvae, aphids, etc. They typically start at the bottom of the tree trunk and walk up the tree, then fly down to the base of another tree and repeat, looking for food. I see them often when I see chickadees and nuthatches. Ridgefield NWR, Feb. 13, 2015.
Canon 5D Mark III, 1/1600, f4.5, ISO 800, 500mm, 10:45 a.m.