Back to the dying aspen, ... I am actually looking forward to this aspen trunk dying (it is one of the largest trees in our yard) and becoming a standing snag (read here for more info). The diameter of this aspen is such that a black-capped chickadee or red-breasted nuthtacth could excavate a nest in its trunk, and there is already some progress to that end. As a result of the aspen borer life cycle, downy woodpeckers excavate the larvae in the late winter/ early spring when the larvae are close to the surface. The holes that the small woodpeckers create later become the beginnings of a cavity that chickadees and nuthatches will enlarge and excavate.
Even though this trunk is dying, this one has suckered and spread (a response to stress) and before long, a new aspen (or several will take its place). So by letting the borers do the work, we get several new aspen, a new snag, a lot of entertainment and wildlife habitat.