Friday, December 16, 2011

Tree Holes

Tree cavities are important as nesting and denning sites for many species of animals.  When I’m out walking, I try to keep an eye on the holes to see if I can spot any signs of life inside.  I’ve enjoyed viewing a wide selection of birds, mammals, reptiles and amphibians using tree holes as a temporary shelter.

Blue Jay Barrens has no shortage of trees with holes that are suitable for habitation by a variety of organisms.  The woods don’t have much to offer in the way of commercial timber trees, but it’s of blue ribbon quality when it comes to offering diverse habitat for animal species.

The majority of tree holes began at the site of dead branches.  The decomposing branch allowed decay to invade the heartwood of the tree trunk.  When the branch finally fell away, it was easy for animals to excavate a nice cavity within the tree.  As the tree tries to grow over the cavity, a ring of growth forms that gives the whole thing the look of a ship’s port hole.

Sometimes a hole is dug though the bark to the interior of a healthy living tree.  These often have a more oval appearance and if they are not maintained, the tree will try to seal the hole.  This hole was about 40 feet above my head, so I couldn’t examine it closely enough to tell for certain whether this was the case here or if it was actually a branch site.

The holes come in all sizes.  There are cavities large enough to accommodate a sprawling raccoon as well as holes that seem perfect for the smallest cavity nesting birds.

Some trees have decay running the length of the trunk.  As more wood decomposes, cavity size increases.  Eventually, the cavity runs the length of the tree.

Sunlight filling the winter woods makes each hole stand out as a dark target, but there’s usually minimal tree hole activity at this time of year.  During the spring and summer, most of these holes become impossible to locate.  After the leaves emerge, dark shadows and dappled sunlight provide an effective camouflage.  My summer walks will occasionally afford me glimpses of tree holes, but unless I make a conscious effort to seek them out, they will most likely remain unnoticed.

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