A den tree is a living tree that has enough decay that a cavity (hole) has developed in the tree. This is usually a hardwood tree and the decay is usually caused by a fungus. Injury to the tree, which allows the fungus access to create the den, is caused by insect attack, lighting strike, drought, flood, equipment scraping the bark, falling tree, or other action that physically injures a tree. Some trees that readily form dens include ash, beech, and basswood.

Den trees are used by wildlife for numerous purposes. These purposes include sleeping, resting, rearing young, roosting, loafing, eating, caching food, escape cover, thermal cover (warmth, coolness, dryness), and temporary or permanent shelter. Den trees can become snags (standing dead trees) which serve similar purposes and are sites for additional cavity construction. Den trees also serve as downed wood (coarse woody debris) which provides habitat, food, shelter, and moisture for many invertebrates and vertebrates. Den trees usually are larger, older, trees.

Some wildlife that use den trees include Raccoons, Louisiana Black Bears, Bobcats, Opossum, Gray and Fox Squirrels, Southeastern Myotis and Eastern Big-Eared Bats, Wood Ducks, Tufted Titmice, Carolina Chickadees, Eastern Screech and Barred Owls, Downy, Pileated, Red-Headed, and Red-Bellied Woodpeckers, Black Vultures, Prothonotary Warblers, Eastern Bluebirds, Armadillos, and honey bees, snakes, frogs, beetles, mosquitoes, spiders, and slugs.

Cavities range in size from greater than 3 feet, for a black bear; 4 inches for Pileated Woodpeckers and Wood Ducks; 3 inches for Eastern Screech Owls; 2 inches for Red-Headed Woodpeckers; 1.5 inches for Eastern Bluebirds; 1 and 2/5 inches for Downy Woodpeckers; and smaller sizes. Threats to den trees include cutting down trees due to development and timber management.

Readings for Den Trees and Cavities

1) “Managing New England Woodlands for Wildlife That Uses Tree Cavities”, Richard Degraaf, Northeastern Forest Experiment Station, U.S. Forest Service, C-171, June 1984.

2) “Frequent Fliers”, Mike Dixon, Texas Parks and Wildlife Department, February 1996.

3) “Cavities in Trees in Hardwood Forests”, Andrew Carey, in “Snag Habitat Management: Proceedings of the Symposium Held at Flagstaff, Arizona on June 7-9, 1983”, Rocky Mountain Forest and Range Experiment Station, U.S. Forest Service, General Technical Report RM-99.

4) “Cavity-Nesting Birds of North American Forests”, Scott et. al., U.S. Forest Service, Agriculture Handbook 511, November 1977.

5) “Wildlife, Forests, and Forestry”, Malcolm L. Hunter, Jr., Prentice Hall, 1990.

6) “The Land Manager’s Guide to the Birds of the South”, Paul B. Hamel, The Nature Conservancy and the U.S. Forest Service, Southern Region, 1992.

Brandt Mannchen
September 6, 2018

Photographs by Duc Nguyen.