Prince Edward County, Ontario, Canada
LIFE AFTER DEATH IN THE FOREST December, 2010/January, 2011 issue The screech owl peeked out at us when I tapped the hollow tree, then sank back down into the darkness of the cavity. At this time of the year, the bird was likely using the hole as a shelter, but could very well have utilized the natural cavity as a nesting site earlier this year. For them, natural cavities are crucial to their survival, as they do not possess the powerful chiselling tools of woodpeckers to excavate their own cavities. Will this hollow tree be here next year for the screech owl, or will it fall victim to the natural elements, or perhaps be cut down in the mistaken belief that doing so is cleaning up the woodlot? When my father and I used to spend a day in the bush sawing trees for firewood some 50 years ago, we thought we were doing the woodlot an important service by cutting down the dead and dying trees. Discarded limbs were thrown into giant brush piles. In the spring, we’d return to the woods with bales of straw, an old tire or two, some old oil and set the brush piles ablaze. The woods now looked tidy with all the limbs gathered up, the dead wood removed and the brush piles burned. If it had been possible to tidy it further with a broom rake, I am sure we would have done that too. In that era, it seemed like the responsible thing to do, to make your woods look clean and tidy. Sunday drives often would be punctuated by glowing comments as we’d pass roadside woodlots, similarly groomed and manicured. “Isn’t that a well kept woodlot?” or, “don’t they keep that woodlot looking nice?” A clean and tidy woodlot was a sign of merit in the eyes of agronomists and property owners alike. Fortunately views are changing when it comes to how a woodlot should be managed. An increasing number of people are recognizing the value of cavity trees and snags. Woodlot practices today selectively remove older trees, providing room for younger trees to grow. Cavity trees are left. So are brush piles for we now know that both of these serve as valuable wildlife habitat. It’s an important step in preserving biodiversity, to interrupt Nature as little as possible. The ideal woodlot, in terms of biodiversity though, is one that is permitted to carry on with no disturbance, where trees, shrubs and plants are permitted to grow, mature, die, fall down and decay in a natural sequence of events. These areas thoughtfully are being set aside where Nature can carry on, uninterrupted, in places like the Menzel Provincial Nature Reserve north of Deseronto, Peter’s Woods north of Cobourg, and even Sheffield Conservation Area south of Kaladar. In Ontario, more than 50 species of birds and mammals depend on cavity trees for nesting, roosting, storing food, as well as for hibernating and escaping predators. It is because of our earlier ignorance about the value of cavity trees that we have experienced a decline in some species, such as the wood duck, and is the reason why active nest box programs are in place. When given a choice though, most cavity nesters prefer natural cavities when they can find them. Birds such as nuthatches and woodpeckers that can excavate their own holes are known as primary cavity nesters, and the list is not very long. Secondary cavity nesters however include a large group of birds including saw-whet owls, barred owls, kestrels, wood duck, goldeneyes, mergansers, eastern bluebirds, great crested flycatchers - the list goes on. Many mammals such as deer mice, raccoons, martens, fishers, weasels, porcupines and black bears also make use of dead trees. Great blue herons, while not a cavity nester, depend on standing dead trees in which to place their nests since they afford an excellent lookout for any incoming predators. Very few colonies of great blue herons will ever be found in live trees. Colonies range in size from a handful of great blue herons to sometimes over 100. Great horned owls and ospreys will also nest in company with the herons. Loose bark on these trees harbours insect life which is fed upon by chickadees, nuthatches and woodpeckers. Even after the trees fall, they continue to provide homes for wildlife. A rotting log provides a somewhat controlled atmosphere for the animals which live there - important as many of these little creatures are unable to control their own body temperatures. Salamanders and snakes make use of decaying logs, and is one place where one might be apt to find the retiring little brown snake. If all wildlife that exists in a balanced forest, from bark beetles to salamanders, could vocalize all at once, the cacophony would be deafening. Nearly everyone is familiar with the pill bug, wood louse or sow bug, common in basements and other damp places. It is a scavenger common to decaying logs, and is unusual in that it is a crustacean. This makes it a close relative of the shrimp, lobster and crab. At some point in its life, the pill bug gave up the watery habitat of its relatives and relegated itself to a habitat with less water but one which is still moist. It needs this as the air around the pill bug must be moist in order for the blood running through its gills to absorb oxygen. Hence its fondness for rotting logs and the moist recesses behind strips of bark on dead trees. In turn, they will provide important food items in the diets of salamanders, frogs, spiders and foraging birds. It is all these little critters, working harmoniously together that will one day return this log to earth, where it will provide rich nutrients for the saplings beside it just beginning their lives. In the late 1980s, when I worked at a conservation authority in Picton, there was a fallen elm tree where I used to take school groups to discuss the importance of rotting logs and how they become their own little ecosystems. I was by that spot just last week, and today there is only a tiny hump not more than a metre in length where that giant once lay and where we used to gather to talk about organisms and how they work. They have devoured that old tree and reduced it to rich humous, providing the smaller trees that now grow there with important nutrients. Something to think about the next time the chainsaw is revved up and aimed at a useless dead tree. For more information on birding and nature and guided hikes, check out the NatureStuff website at www.naturestuff.net Terry Sprague lives in Prince Edward County and is self-employed as a professional interpretive naturalist.