If you talk to your dentist, you’ll certainly be told that cavities are bad, but your perspective might change if you were a bird. I am not sure if this Red-bellied Woodpecker (Melanerpes carolinus) was checking out potential nesting sites yesterday morning at Occoquan Bay National Wildlife Refuge or merely looking for insects, but it sure did give this tree cavity a careful examination.
There was definitely no need to fill this cavity.
© Michael Q. Powell. All rights reserved.
Mike Powell 
Beautiful photo, Mike!