Cavity Trees

We’ve looked at needle-leaved and broadleaved trees this winter but standing and fallen dead trees make enormous contributions to PEI’s forests, too!

Trees die naturally from a variety of causes: old age, disease, insects, fire, weather damage, or environmental stress, among others. The death of a tree is part of the life of a forest and is necessary for the survival of everything from plants, lichens, and fungi to insects, birds, and mammals. 

Insects such as Bark Beetles and Carpenter Ants are among the first animals to make their homes in dying and dead trees. That’s good news for insect-eaters such as Chickadees and Nuthatches who find a meal under loose bark, and Woodpeckers who start excavating the wood to get at tasty insects inside. 

Woodpeckers are among the few animals we have that are capable of starting holes in trees – both to find food and build nests – and are called ‘primary cavity nesters’. Chickadees and Red-breasted Nuthatches are also considered primary cavity nesters, although they can’t excavate hard wood like Woodpeckers can; they need it to have aged and softened a bit (and aren’t too proud to use an existing cavity if one is available). 

Good real estate is a valuable commodity, and an old Woodpecker nest or natural cavity doesn’t stay vacant for long. ‘Secondary cavity nesters’ are animals that rely on tree cavities but can’t make their own. On PEI, we have dozens of such species, including birds, mammals and beneficial insects. Common examples include American Kestrels, Brown Creepers, Owls (Barred, Great-horned, Saw-whet), Tree Swallows, White-breasted Nuthatches, Wood Ducks, Flying Squirrels, Red Squirrels, Red-backed Voles, Raccoons, Bats, and Bees. 

Cavity trees eventually fall to the ground, but their importance continues. Salamanders and Frogs appreciate the moisture-rich rotting wood, along with the insects found in it. Male Ruffed Grouse use fallen trees as drumming logs to claim territory and attract a mate. Hollow trunks of downed trees provide dens for Raccoons, Foxes, and Coyotes, along with nest sites for Mink, Weasels, Mice, and Voles. In all, I can think of more than 30 species of amphibians, birds, and mammals on PEI that use dead trees, and that doesn’t take into consideration insects, fungi, mosses, and lichens. If those were included, the tally would easily reach many hundreds. I’ve met dead trees that hosted entire ecosystems in miniature! 

Next time you pass a standing or fallen dead tree, take a moment to appreciate the contribution it’s making to PEI Untamed!