Odd Behavior for a White-breasted Nuthatch, by Bruce Wunderlich

Video by BWD Production Director Bruce Wunderlich.
While photographing nuthatches bringing nesting material to a cavity, I noticed a male bring a significant chunk of something. Zooming in, it appeared to be rust-colored fur from an animal. He carried this material to a fork of a tree, where he pounded it with his powerful little bill. I assumed this would probably become “tenderized” nesting material, but no. What he did next was perplexing; I had never seen or even heard of this behavior before: With the fur in his bill, he began sweeping around the cavity opening with a rapid back and forth motion, as though he was sweeping the floor! Later, I watched him use an insect in the same motion to sweep the entire circumference of the hole.
It has been theorized that this behavior is intended to protect the nest from predators! Squirrels leave a scent trail on the branches of trees that they use to travel around and find their nest. This fur-sweeping motion was the nuthatch’s attempt to cover up this scent to prevent the squirrels from returning to this nesting cavity and reclaiming it.

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It looks like its anting the tree