Input (grade 13): Birch bark or birchbark is generally understood to be the bark of the Paper Birch tree (Betula papyrifera), or sometimes of related species such as Gray (Wire) Birch (Betula populifolia).
Output (grade 9): Birch bark or birchbark is usually the bark of the Paper Birch tree or sometimes of similar trees such as Gray (Wire) Birch.