What About A Tree Swallow Ladder?

Significant numbers of tree swallows perish in bluebird and other bird boxes each spring because they are not able to exit.

For any nest box made with relatively smooth lumber, it is important to have a “ladder” beneath the entrance hole to enable tree swallows to exit. Horizontal grooves can be sawed, or a small strip of plastic gutter guard works great and can be stapled beneath the entrance hole.