Snags and healthy ecosystems

Standing dead trees, called snags, provide birds and mammals with shelter to raise young and raptors with unobstructed vantage points.

Over five hundred  species of birds, three hundred species of mammals, four hundred species of amphibians and reptiles, and nearly all fish–because of the beneficial effect of snags on watersheds–benefit from snags for food, nesting, or shelter.

Only thirty bird species are capable of making their own nest cavities in trees. Another eighty animal species depend upon previously excavated or natural tree holes for their nests.

The insulation of a tree trunk home allows many animal species to survive high summer and low winter temperature extremes.

Tree cavities and loose bark are used by many animals to store their food supplies.

Insects living in dead wood eat thousands of forest pests which can harm living trees.

Fish and amphibians hide under trees that have fallen into the water.

Woodpeckers and creepers feast on the wood-eating insects and provide "sawdust" for ants to process. Deer eat the lichen growing on the trunks.

Source: Snag Facts with Impacts, US Forest Service