When superstorm Sandy ripped up the East Coast, it caused devastation to many human communities, but it also destroyed habitat for wildlife, including a lot of standing dead trees, also known as “snags.” While we humans may see snags as a threat to human life or structures, or just as an eyesore, to many species of wildlife this last stage in a tree’s life provides critical habitat.
Past the point of being able to produce leaves, flowers or fruit, snags still offer shelter and a host of other services to animals. While snags can look stark, untidy and even depressing to the human eye, they’re like a million-dollar condominium complex to other species. Cavities in snags offer protection from predators, precipitation, wind and extreme temperatures. They also serve as places to rest, preen, store food, hibernate, perch, drum to signal ownership of territory, watch for predators and roost at night. Among the species taking advantage of such a versatile natural phenomenon are woodpeckers, eagles, chickadees, bluebirds, swallows and swifts, ducks, owls, warblers, hawks, beetles, tree frogs, skinks, rat snakes, bats, squirrels, mice, bobcats and foxes.
Snags are particularly important to wildlife species that raise their young in tree cavities. In fact, 30 to 45 percent of bird species nest in tree cavities. While some species, such as chimney swifts, have adapted to man-made structures as substitutes to tree cavities, many won’t nest elsewhere and would become extinct without them.
Trees can become snags in many ways. Age or damage from weather or insect infestation can start them on the way to decline, with those who pray on the insects soon following. Once the bark is breached, bacteria and fungi can also speed the tree’s demise.
Woodpeckers are the great condo builders among forest wildlife. In pursuing insects feeding under the bark, they widen the holes the insects make. While serving as exterminators that can save a tree from serious insect infestation, once woodpeckers start drilling, they sometimes don’t stop and continue to enlarge a cavity to suit their nesting needs.
Bigger woodpeckers and other wildlife may continue to enlarge the hole until it can house a raccoon, fox or even a hibernating bear. Loggers in the northwest have been known to cut out sections of trees with hibernating bears in them, leaving that bear condo on-site and carrying off the rest of the tree.
One large, elderly ash tree down by one of the ponds where I live had been on its way to becoming a snag for quite a while. In the process, it had become a spectacular housing project for wildlife, with the base of the trunk – which is more than two feet in diameter – hollowed out and myriad holes varying of varying sizes up to 6 inches in diameter going up the trunk and out into the limbs. Late in September, most of the tree finally blew over in a windstorm.
In examining the cavities in the portion of the trunk that now lay on the ground, I found most filled with a thick layer of sawdust and woodchips that would have been cozy for anybody’s young. Most of the cavities were clean and tidy with just a hint of bird lime here and there.
While cavity nesters may lose a home when a snag goes down, nature has a way of recycling everything. Even on the ground, a snag offers food and shelter to earth-bound species, such as snakes and beetles. And as it continues to decay, it releases carbon and other nutrients it’s been storing back into the energy cycle, which in turn fuels the next generation of trees and other plants and animals.
While some of us might find dead trees ugly, others see a stark beauty in them. With leaves, and sometimes bark, gone, the “bones” of the tree are visible and can add a simple elegance and grace to a landscape as well as a reminder of the continuing cycle of life.