Autumn Wood Cutters Can Save A Community

Heidi Youmans, FWP Small Species Bureau Chief and Diane Tipton, FWP Statewide Information Officer

Thursday, September 15, 2005
Comprehensive Fish & Wildlife Conservation Strategy (CFWCS)

This article was Archived on Saturday, October 15, 2005

Standing dead trees, or snags, may seem to be scraggly eyesores, of value only as firewood. But snags are important pieces of the natural world. Sparing some larger dead trees from the chain saw preserves habitat for a community of cavity-dwelling birds and other wildlife species.

A snag is a good place to observe pygmy owls, woodpeckers, squirrels, pine martens or raccoons. The species you see depends upon the snag tree’s height, circumference, stage of decay, and location.   Some birds, like the woodpecker, will hammer out a dwelling soon after the tree dies, while other birds and small mammals may come later and use spaces abandoned by earlier inhabitants.

Over decades, a single snag may nurture generations of birds and help reduce the number of insects in the area.

Birds that use snags as a source of insects include owls, violet-green and tree swallows, wood ducks, common and Barrow’s goldeneyes, buffleheads, hooded mergansers, nuthatches, kestrels, Vaux’s and chimney swifts, flycatchers, chickadees, brown creepers, house wrens, and winter wrens. Several species of bats also use snags, as do squirrels, pine martens, raccoons and porcupines. Even the adult Montana state butterfly, the mourning cloak, may spend winter in a hollow tree.

A standing dead tree also gives life to tiny wildlife and even plants.   Decaying snags are important to fungi, moss, lichens, ferns, invertebrates, reptiles and amphibians. Creatures use the woody material from snags for foraging, thermal cover, denning, nesting and hollowed out pieces serve small creatures as short but safe travel tunnels. A decaying snag adds woody material to the forest floor that holds and slowly releases moisture and adds nutrients essential to the growth of new trees.

  In populous states, woodcutting on public lands is restricted to trees that have already fallen, so that standing snags are reserved for cavity-dwelling birds. In Montana, the state leaves it up to woodcutters, landowners and others to take steps to preserve snags for wildlife.

A snag goes through three stages identified by the Forest Service. When a large tree dies it is called a "hard snag," because the bark is still intact and the tree has firm heart and sapwoods. It is attractive habitat for woodpeckers.

Later, it decays into a "soft snag" which means some bark remains and there is softening wood that is easier to penetrate and shape. At this stage, it may attract chickadees and nuthatches, for example. A soft snag becomes a "buckskin snag" when the bark is missing and the wood softens even more, attracting species that don’t make their own cavities but rely on those carved out earlier and abandoned. These second-stage cavity dwellers include bats, western and mountain bluebirds, barn owls, squirrels, martens and raccoons.

As it decomposes, the top of the tree decays and breaks off, so the snag becomes shorter and shorter as it adds woody material to the forest floor.

If you are out cutting wood this fall or just rambling through the forest, take a minute or two to find a standing dead tree with a nesting hole or rotted-out hollow. Take a break there and view the community of cavity-dwelling birds and other small species that generally surround a snag.

For more on the species mentioned here and on other watchable wildlife, see FWP’s Comprehensive Fish & Wildlife Strategy and Montana’s Animal Field Guide.

If you consider a dead tree an eye-sore, don’t be surprised when taking a second, closer look to see instead a rich wildlife habitat.

PRESERVING SNAG TREES FOR WILDLIFE   HABITAT

Here are some tips on how to help preserve snag trees for wildlife habitat.

* When cutting firewood, avoid cutting dead, standing western larch, ponderosa pine or black cottonwood snags in areas where they are uncommon. Alternative firewood choices such as lodge pole pine, spruce and sub-alpine fir trees are not as important for cavity-nesters.

* Avoid cutting snags that show evidence of bird use such as nest holes, bird excrement stains or woodpecker drill holes.

* Avoid cutting live or dying trees with broken tops, since they are prime candidates to become snags that are particularly desirable to wildlife.

* Avoid cutting snags that have loose bark. Species such as winter wrens and bats nest or roost behind loose bark.

* Avoid cutting trees that show evidence of heart rot. This softer wood is attractive to cavity dwellers.