Disease, lightning, wind, and time change trees. They transform even the oldest trees into snags, or standing dead trees. Snags are home to many birds and mammals. Pileated woodpeckers chip away the wood to feed on insects under the surface. Hawks look over the land from the broken tops of trees.
Bats roost under the loose bark.
At night they come out to feast on flying insects. The soft snags are not very strong. Windstorms, lightning, and other natural elements often make them fall to the ground. When these ancient giants die, they fall to the ground. This creates openings in the forest.