These secondary nesting birds comprise up to one third of the breeding birds found in some forests. Most cavity-nesting birds consume large quantities of insects each year. Insect outbreaks often attract cavity nesting birds. Snags are used in numerous other ways. Squirrels and other small mammals use dying and dead trees as foraging sites, to store winter food supplies and for roosting and denning.
Bats use loose bark and hollow tree trunks for roosting.
The death and eventual falling of trees provide forest openings that encourage regeneration of shrubs, trees and grasses. This leads to improved habitat for species such as deer and small mammals. The number of snags in a forest varies. The creation of new snags depends on agents of mortality including insects, disease and fire. Tree death in the forest is patchy, episodic and grouped reflecting the ways in which natural disturbances work.