Ecological Forestry
The Importance of Wildlife Trees

Dead standing treess are called snag or wildlife trees.
They are home to a variety of creatures.

"Reliance on bird boxes requires the placement of many types and sizes of nest boxes at various heights and densities throughout the forest. The boxes must be constructed, installed, cleaned and replaced periodically. The cost would be formidable and the results probably less successful than if snags were present."

USDA Forest Service, Wildlife Habitats in Managed Forests

The absence of snag trees (dead or dying trees used by a wide variety of wildlife for nesting, feeding and roosting) is another reason clearcuts are harmful to wildlife. Many species of birds excavate cavities in decaying trees (or use older excavations) to nest in. The following birds make use of cavities for nesting on Prince Edward Island:

• wood duck,
• hooded merganser,
• merlin,
• American kestrel,
• eastern screech-owl,
• barred owl,
• northern saw-whet owl,
• pileated woodpecker,
• common flicker,
• yellow-bellied sapsucker,
• hairy woodpecker,
• downy woodpecker,
• black-backed woodpecker,
• three-toed woodpecker,
• tree swallow,
• black-capped chickadee,
• boreal chickadee,
• white-breasted nuthatch,
• red-breasted nuthatch,
• brown creeper and
• winter wren.

Wildlife trees can be created by girdling.

Others, like the bald eagle and osprey, often build their nests in dead or broken-topped trees. Hawks use snag trees as perches, while the loose bark of dead trees is an ideal roosting spot for little brown bats and spring peepers. Raccoons, red squirrels, northern flying squirrels and deer mice use cavities for nesting or denning.

Snags also provide habitat for ants and other important food sources for many birds. Remember that snags are not just home to birds and mammals - insects and other invertebrate, as well as fungi recycle dead tissues of the tree into new life. Even-aged, young softwood stands have a poor diversity of insects compared to older growth. In these stands, most insect species are plant eaters, while older forests have a greater abundance of predator and parasite species. Reducing bird and mammal populations that mainly eat insects can seriously affect the stand's ability to resist insect attacks.

1. Again, the rule is no large clearcuts - even recent changes towards leaving select snag trees in clearcuts is unacceptable. Most are shallow rooted and too exposed to the wind. They will blow down within a few years, leaving the site without any snag trees for a long time.

2. When doing selective harvesting, make sure to leave a sufficient mix of snags in the forest. We do not know exactly how many to leave, but according to the Forest/Wildlife Guidelines and Standards for Nova Scotia, "Large trees over 50 cm (20 inches) diameter at breast height are better for cavity users because they provide habitat for both large and small wildlife species. Trees smaller than 20 cm (8 inches) dbh are of limited value to cavity nesters and will not provide nesting habitat for woodpeckers larger than the downy woodpecker, our smallest." The guidelines call for leaving 10 snags per hectare (4 per acre). So we would want at least that many continuously available in the forest. This means that young and middle age trees must be left to become future snags, not just the four old trees you leave for today. This is almost impossible to do in a clearcut.

Snag or Wildlife tree.

3. If your woodland lacks snags but has large living trees, you may want to speed up the natural process and create snags by girdling a few trees, both coniferous and deciduous. With an axe or chainsaw, remove a complete ring of bark and cambium layer by axe or chainsaw to prevent the sap from rising in the tree.

4. Plan to allow some trees to become quite large. Studies on the pileated woodpecker in Oregon suggest that size of nest and roost trees is an important consideration. Research showed the smallest diameter nest tree to be 54 cm (24.5 inches) while the mean diameter was 84 cm (32 inches). This is hard to achieve on short-rotation plantations.

5. Make sure that there are logs on the ground or larger trees that have blown over throughout the forest. They provide drumming logs for ruffed grouse; perches for hawks and squirrels; and are full of insects and other invertebrate that serve as a food source for animals.

Fallen trees also are excellent nursery sites for yellow birch and hemlock seedlings, offering a moist environment and nutrients that are released slowly.

ECO-PEI - Macphail Woods Ecological Forestry Project a member of the Island Sustainable Forest Partnership Cooperative with assistance from Natural Resources Canada - Canadian Forest Service and the Model Forest Program have put together a series of Wildlife enhancement sheets on Prince Edward Island.

• Dead Trees

This series of webpages is based on the booklet "Wildlife and Woodlands - What you can Do !" written by Gary Schneider. This booklet reflects the views of the Environmental Coalition of Prince Edward Island independent of federal and provincial government departments. If your interested in receiving a hardcopy of this booklet, please see our publications page. Web development and maintenance by Chris Martin.