plagued birch
We think they are white birch. The holes start at the bottom of the tree, no sap, maybe some sawdust like wood at the opening of the holes. Dan thought it was the woodpeckers at first. But I don't see them at the bottom of trees. They may be an inch to 4 or so inches apart, 1/8th of an inch or smaller in diameter, and seem to be on the south side of the tree. Two of the trees have these holes. Also after comparing with other woodpecker damaged trees the holes aren't the same. Thanks for writing.