A snag is any dead or dying standing tree. Snags may develop cavities which either occur naturally or are excavated by birds and mammals. Over 85 species of North American birds,35 of which occur in the Northeast, use cavities in dead or deteriorating trees.
Snags also provide essential habitat requirements for cavity-using amphibians, reptiles and mammals.
Snags are used for nesting, shelter and feeding sites. The removal of snags can negatively impact wildlife populations that are dependent on them as essential habitat components. Cavity nesters evolved in unmanaged forest stands where snags developed naturally. Snag and den trees are becoming short in supply as forests are being intensively managed, whether through cordwood cutting, timber management or land clearing. These activities tend to accelerate the removal of existing snags and diminish the probability of trees ever becoming large enough to serve as possible snag or den trees.