Holes in living and dead standing trees, also known as cavities, are an important part of the habitat of many animals. More than 40 species of wildlife use cavity trees for nests, where they bear their young, or shelter. Black-capped chickadees, eastern bluebirds, and downy woodpeckers will use trees less than 8 inches in diameter. The chickadee is a primary excavator, an animal that creates a cavity to use for itself, but leaves it behind eventually for some other animal to use. Wood ducks, turkey vultures, red squirrels, porcupines, and long-tailed weasels use trees larger than 18 inches, and little brown bats, raccoons, and black bears need trees larger than 24 inches in diameter.
Dead trees lying on the ground also are important.
They provide feeding sites for rodents, shrews, black bears, and woodpeckers, as well as winter shelter for 17 species of New Hampshire mammals. Amphibians rest in the cool, moist micro-habitat that dead trees provide. In streams, the downed logs create pools and riffles for fish habitat, and create basking and nesting locations for turtles, waterfowl, mink, and otter. Juncos and winter wrens nest in the roots of upturned trees. Dead and down woody material also provides habitat for many lower organisms such as insects and other invertebrates, mosses, fungi, and lichen.