Huh, you learn something new every day. I've seen it plenty in Vermont and New York, and in Alaska as well, so I assume it probably grows anywhere in between you find birches. As far as I know, no fungus that grows off the side of a tree is poisonous. Now the ones growing on the ground are another story, got sick as a dog once from something I thought was a puffball, before I learned that puffballs should always be white in the center. They were tasty though.