Chickadee behavior

During my visit to Springbrook last Thursday, I noticed two Chickadees flying in and out of what looked like a nesting hole in a tree. I wasn't sure what they were doing.

  

  

  

  

  

  

  It wasn't until I saw these photos on my computer that I saw something unexpected.

  

  

They were taking wood chips OUT of the hole. Was it for their own nest elsewhere? Were they cleaning out this hole for a nest? This is what I learned at the Sialis site :

They are cavity nesters, usually selecting a site in a rotted part of a tree, especially in stubs, snags and rotted out knotholes in forests and woodlands. Chickadees can excavate their own nest cavities, removing wood chips and dumping them away from the site to avoid attracting predators. They may use old woodpecker holes or nestboxes.

They prefer a side entrance, and if the stub or branch is slanted, the entrance is often placed on the lower surface, providing protection from the elements. Very rarely they may nest in a hole in the ground like Mountain and Chestnut-backed chickadees.

This did not look like a rotting tree. Perhaps a woodpecker had made the hole. What do you think?