Aside from endeavoring to identify every tree I walk past when I’m walking my beloved four-legged companions, Susie Q and Maggie Mae, I get a pretty big kick out of seeing snags and downed logs on people’s property. Yes, I’m that person looking and scouring over your landscape, but I’m not ruminating over your grass or shrubs, I’m thinking: “Wow, what a great looking dead tree you have tucked over there next to the forest edge, I sure hope you plan to leave it!”
Why? Snags, cavity trees, and downed logs provide critical habitat for a wide variety of wildlife species, and are thusly important components of the forest ecosystem. Snags are standing dead or dying trees, and downed logs are simply a former snag tree than has fallen and is now on or near the forest floor. Cavity trees are live trees with holes or other structures big enough to shelter animals. This includes trees with only limb cavities. Limb cavities are more important to some wildlife species than large hollow trees.
Snags are created when a tree is killed by lightning, storm breakage, fire, disease, insects, or a variety of other factors. Almost every part of a dead tree, at varying stages of decomposition, can be used for nesting, roosting, foraging, perching, and territorial displays. As the snag decays and the wood softens, woodpeckers (primary cavity nesters) excavate cavities for nesting and roosting. Thereafter, many other animals (secondary cavity users), including songbirds, owls, bats, raccoons and squirrels, use the cavities for nesting, roosting, or storing food supplies. Exposed high branches of snags are perfect for raptors to perch and watch for potential prey.
When a snag falls it becomes a downed log, which provides cover and foraging areas for many reptiles, amphibians, small mammals, birds and invertebrates. Decaying logs attract insects, fungi, lichen, and moss, providing a food source for wildlife. As logs decay, they replenish soil nutrients and act as “nurse logs” for new tree seedlings to sprout. In North Georgia, our yards tend to be more natural and many folks either live in a forested area on along the border of one. But, as our population grows and more development occurs in natural areas, a continuous supply of snags and downed logs becomes evermore important, as these resources must be maintained to sustain populations of animals that depend on them.
Approximately 20 percent of the entire forest fauna rely on dead and dying wood for food or other habitat essentials such as cover and space. Fortunately, simply leaving or protecting snags and downed logs is a simple, low-cost means of wildlife habitat improvement. For those who are interested in scouring your yard for them, it is important to provide snags of various sizes. Generally, large snags (>10 inches diameter at breast height) are more valuable than small snags because they can be used by a wider variety of species.