Yellow-bellied Sapsuckers are named for their behavior of drilling small holes in trees then drinking the sap that runs into the wells. They get most of their food that way but also feed on insects they find under tree bark.
I’ve seen them peck at bark, mostly on the rough-barked trees and was surprised to see this one bobbing into a tree cavity. He was just about disappearing from my view as he reached in.
I didn’t see what, if anything, the Sapsucker was finding, but he kept at it for longer than I watched.
Yellow-bellied Sapsuckers visually blend into the surface of the rough-barked trees. These two images were taken in different places over a month apart.
I heard the tat-tat-tat of pecking at the bark first, then watched for the flash of red to help me spot them. Sapsuckers tend to spiral around the tree looking for food, sometimes at a pretty fast pace leaving the photographer to guess where they will pop back around.