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Why Dead Trees are Important to Wildlife

There's no denying they don't seem to offer much that property owners find appealing. They're messy and leafless. Insect-infested. And, in some instances, even threatening. But landowners should know that the benefits dead trees or snags provide wildlife are immense. In fact, in Pennsylvania today, dead trees are in higher demand for certain wildlife species than living ones, mostly because there are so few of them.

Prior to European colonization, much of the state was covered by a dense forestland that had a substantial number of dead and dying trees. It was a great time for cavity-nesting birds and squirrels. The state's settlement, of course, would change that eventually. And to this day, development continues to swallow more wild lands and often forestland or woodlots. Dead and dying trees typically are some of the first to be cleared.

The main problems developers and some property owners have with dead trees and snags are their unattractiveness and the usual threats associated with their deterioration. But wildlife managers familiar with the important habitat dead and dying trees provide forest ecosystems believe these trees deserve more respect than they're getting. They can - and should - be managed with the same considerations live trees receive.

Dozens of wild birds and mammals use tree cavities for shelter, resting or nesting. Some excavate their own cavities in the decaying wood of dead and dying trees. Others wait for a woodpecker to do the work and then occupy and enlarge the cavity.

These cavities in dead and dying trees - as well as some living trees - are invaluable to bluebirds, American kestrels, wood ducks, flickers, pileated woodpeckers, chickadees and many other species. Their limited availability makes each one a precious commodity in any forest, woodlot or backyard.

The natural benefits provided by dead and dying trees extend beyond cavities in the trunk. The separating or peeling bark can shelter resting bats during daylight hours, or provide habitat for insects that many wild birds consume. The bare, weather-worn branches are favored hunting perches for hawks and owls. After the tree falls, it provides shelter for amphibians, reptiles, birds, mammals and insects. The tree's decaying debris also returns nutrients to the soil, ultimately strengthening the forest's ability to support life.

It doesn't matter whether a dead tree is standing and serving as an insect smorgasbord for woodpeckers, or laying on the forest floor and providing a silent passageway through the noisy leaf litter for hunting red foxes and habitat for amphibians, every woodland needs and benefits from them. They not only provide unique habitat and habitat diversity, they also are part of the natural order that all successful forest stewardship programs strive to promote.

About half of Pennsylvania remains forested, and slightly more than half of that forestland is dominated by large trees. A small percentage of these large trees are dead, deteriorating or harboring cavities that birds and mammals use for dens or nest sites. To help offset this disparity, the Game Commission has been manufacturing nesting boxes for everything from bluebirds to wood ducks for years at its Howard Nursery in Centre County.

In recent years, Howard Nursery has produced in excess of 2,000 bluebird boxes, 5,000 bluebird box kits, hundreds of wood duck, kestrel, barn owl and bat boxes for placement on State Game Lands and other lands enrolled in the Game Commission's cooperative public access programs.

Other beneficiaries of these wildlife boxes include house wrens, tree swallows, flying squirrels, screech owls and woodpeckers.

Bluebirds and wood ducks, in particular, have benefited greatly from nest boxes. Both species - reeling from insufficient nesting sites for years - have rebounded to respectable numbers in Pennsylvania and elsewhere as a result of thousands of nesting boxes being placed afield by wildlife managers, hunters and boy scouts, to name a few.

The Game Commission's ongoing nesting box program and the efforts of caring conservationists have helped many native cavity-nesters exceed the limitations imposed by insufficient natural nesting sites. But nesting boxes are only part of the answer to Pennsylvania's shortage of dead trees and snags. We need private landowners to understand the importance of dead and dying trees and the need to conserve as many as possible.

The Game Commission has a State Game Lands tree policy in place that requires snags and den trees to be retained on timber harvest areas. This retention policy allows for these valuable wildlife havens to be retained and incorporated into future plans for the stand. The agency's management philosophy is guided by creating a balance of habitat types on State Game Lands, providing the immediate habitat of the dead trees while providing the essential elements of early successional type habitats necessary for species such as ruffed grouse and American woodcock, along with the highly sensitive species such as golden-winged warblers.

It has been estimated that dead trees and trees that contain decaying wood provide important habitat for about 25 percent of the forest wildlife species in the northeastern United States. Considering that, it quickly becomes obvious that nesting boxes only can help ease the demand. Moreover, nesting boxes just don't provide the insulating qualities that tree cavities offer in winter. They are mostly a warm-weather solution to the plight of cavity-nesters, not a panacea.

A dead tree can stand for decades, providing critical shelter and food to myriad species. It's a habitat high-rise that attracts considerable attention in any wildlife community or ecosystem. What determines how long the tree will stand includes factors such as whether it's surrounded by other trees that will reduce wind and impede sunlight, the species of tree (hardwoods such as oak typically remain upright longer), and the type of terrain or area in which it grew. Trees near streams seem to take more abuse from the elements than other places because they have greater exposure to water and shade.

If a dead or dying tree isn't threatening your residence, picnic pavilion or roadway, the Game Commission recommends leaving it to nature and the benefit of wildlife. It won't be long before you'll see its worthiness to wildlife and begin to appreciate the additional character it affords your backyard or woodlot. If you're into wildlife, you should be into dead trees.

When a dead tree poses threats to a nearby structure or activity area, landowners should consider stripping down the snag to reduce or eliminate its potential to cause trouble. Using a hydraulic cherry-picker - never climb a dead tree - remove part of the tree's top and/or branches to remedy the risk. Even a branchless trunk - cut to a height that addresses the landowner's safety concerns - has wildlife and ecological value, and should be considered over removing the tree entirely.

Remember, as a rule, dead trees don't come down in a hurry, particularly hardwoods. So as long as safety isn't a concern, let nature take its course. The tree will become a wildlife magnet and will be worth is weight in gold to the creatures using it. Let that dead tree stay on. Rest assured, it will make wild friends fast.