Life After Death In the Forest

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.