Elaine, I know my brush piles are inhabited by chipmunks, snakes and possibly rabbits. The Carolina wren loves foraging through the piles as do several other species of birds.

And don't forget the frogs...after a pile has been there long enough to have a layer of broken down material underneath, the toads will move in as will the tree frogs when the weather cools. I learned this the hard way a few years back in early spring while relocating a brush pile of my own. There were grey treefrogs balled up in the lower leaf/debris layer and I wonder how they liked such a rude
and premature awakening.
And brush piles evolve, too. The biggest one we had started out as a pile nearly ten feet tall and 30 feet long just down off the bluff in the back yard. It housed oppossums and snakes and all manner of creatures and even once served as a jungle gym for five or six gangly young turkeys and one worried old hen. Although some might consider them eyesores, I couldn't disagree more. Our tangle of trunks and limbs more than once offered animals a bit of refuge during the yearly floods since it was elevated above the forest floor. That was 12 years back and now it is a four-foot high fertile pile of dirt with elderberries, nettle, jewelweed, ferns, young trees and bluebells adorning its flanks--most of these having washed in during one flood or another-- with one cypress thrown in for good measure by yours truly.

I think a brush pile is essential to creating a habitat for animals, although I realize that not everyone can have them (neighbors or lack of space). My brush pile contains piles of all my invasives, since I do not want to throw them into the compost pile. Also any sticks or branches which are just too large to compost.

There are plenty of things living in it, I believe a fox family is occupying a burrow under it, and I believe a groundhog made the burrow a few years back. Rabbits, birds, snakes and plenty of different insects inhabit it.

Another good thing to have is a rock pile - we all find rocks while gardening, throw them together and many species will consider you their best friend.