Future Nesting Home

The woodpeckers have been working on this stump for a couple of years. It recently has taken on the architectural shape for a bird's home next season... I guess that is what it's for?
The wire that enclosed it is a tall cage that had been used to protect a tree from the deer and now allows a bittersweet vine to safely live there. The deer like that too, alas, but the cage gives something to climb on.