I apologize that no one has responded to your question sooner. Different experts come online at various times. I just came online and saw your question. My name is ***** ***** I’m a biologist with a special interest in trees. I'm sorry to hear of this incident.
It would be extremely rare for a woodpecker to damage a tree enough to hurt or kill it. What is usually occurring is that the woodpecker is feeding on insects in the tree's bark or wood. Many times these insects are harmful to the tree.Woodpeckers will also drill on a tree that is weakened by a fungal infection. For the most part, woodpecker damage to the tree is insignificant and nothing to worry about. Once in awhile, the birds will drill so close together that the tree is in danger of being girdled.To prevent that, you can loosely wrap the tree trunk in burlap, and/or smear it with a sticky substance such as Tanglefoot or Bird Stop (available in garden centers and online). These measures will discourage the woodpeckers. You can confirm this information here:http://www.arborilogical.com/tree-articles/woodpecker-damage/
For the sake of the tree, it's best not to fill the hole. That often seals infection inside the tree, and can even lead to its death. The first thing to do is check the hole for an insect infestation. I would be especially concerned about birch borers.Bugs are often the reason woodpeckers go into a tree. If you find any, eliminate them before you do anything else. Next wash the holes with a mild soap and water, then rinse it thoroughly. Let it completely air dry. Then spray it with a fungicide, and nail or screw a protective cover over it. You can use sheet metal, window screen, or hardware wire. The purpose of the cover is to keep the woodpeckers and other birds out so they can't cause further damage. If you have eliminated the insects and any fungus, the tree will heal itself. If you're not sure of what is weakening the tree and attracting the woodpecker, you may want to consult a certified arborist. That would give you the greatest chance of saving the tree. There is a directory of them on this website:
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