Fifty years ago a friend of mine bought an old two room school house in
the Sierra foothils of CA.
I help in the renovation. Under eaves there was a row of woodpecker
holes and when we pulled
off the siding a cascade of acorns came falling down. The WP had
insulated the walls with acorns.
They are not too bright as they hope the acorns will attact bugs and
become infested with worms.
If they do this in a tree, the acorn stays in the hole and does
produce worms. They could not figure
out tha the ones they put in the building just went away.
CP