Woodpeckers can cause extensive damage to nest boxes. Usually the damage is limited to the entrance hole as a persistent woodpecker will attempt to enlarge the hole permitting entry. Metal portals are available which are mounted over a nest box's entrance hole to limit hole enlargement. This photo shows such a metal portal. Note that enlargement of the entrance hole still occurred, but the metal portal remains and retains its original size.

Note also that the very determined woodpecker still caused significant damage to the box's wood portal.