Most people walking a nature trail probably wouldn’t give a second thought to a hole in an old tree. A few days ago, while hiking through a small nature preserve near my home, I stopped to look more closely at this one.
As a biologist, I immediately recognized it as a cavity likely excavated by a Pileated Woodpecker. These impressive birds, nearly crow-sized, use their powerful bills to carve nesting and roosting cavities into dead or declining trees.
But what caught my attention wasn’t just the woodpecker. It was the reminder that this hole represents something much larger: the importance of leaving some dead and dying trees standing whenever they do not pose a safety risk to people, homes, or other structures.
Wildlife biologists often refer to birds as either primary cavity nesters or secondary cavity nesters.
Primary cavity nesters, such as Pileated Woodpeckers, Downy Woodpeckers, and Hairy Woodpeckers, create their own nesting cavities. Secondary cavity nesters, however, cannot excavate cavities themselves. Species such as Chickadees, Bluebirds, Tree Swallows, some owls, and even certain ducks depend on cavities that have already been created by woodpeckers or formed naturally through decay.
In many ways, woodpeckers serve as nature’s carpenters. Their work provides homes not only for themselves, but for an entire community of wildlife that follows.
And the story doesn’t end with birds.
Tree cavities may also shelter squirrels, bats, flying squirrels, raccoons, insects, salamanders, and countless other creatures. What appears to be a simple hole in a tree is actually a valuable piece of habitat.
As people, we often focus on living trees—and rightly so. But standing dead trees, sometimes called “snags,” play an equally important role in healthy ecosystems. A forest without a few snags is a little like a neighborhood without apartments. There simply aren’t enough places for many residents to live.
The next time you encounter an old tree with a cavity along a trail, pause for a moment. What looks like decay may actually be a sign of life. Someone built that home, someone may be living there now, and many others may depend on it in the years ahead.
Sometimes a hole in a tree tells a much bigger story than we realize.
— Ron Dodson
The Nature of Things 🌿