This is a dead ash tree, that gets a lot of woodpecker traffic. My yard has nesting sites used by Hairy, Downy, and Red-bellied woodpeckers; also Northern Flickers. Just this past summer, I’ve been seeing Pileateds visit the tree, so with luck they’ll be the ones excavating this out next spring.
This is a burrow in the ground under my Callery pear tree. I’ve never seen what lives there, but I see a long passage of sunken ground coming off this hole, so the complex must be spacious. It may be only rabbits, but it would be nice to have a badger or a weasel.