The invasion of a stream by beaver usually results in an ecological succession that provides habitats where increased numbers of plants and animals can exist. The water is utilized by stock, deer, waterfowl, muskrat, raccoon, mink, quail, pheasant, and many other kinds of wildlife. The increased variety and amount of vegetation that normally grows around a biologically balanced beaver pond furnishes habitats for various insects, many of which are used as food by fish in the pond. Shrews, meadow mice, and other small mammals invade the area and become established. Ducks and other waterfowl find nesting sites around the ponds.
Woodpeckers drill other holes in the dead trunks.
Those holes provide essential nesting sites for tree swallows, crested flycatchers, bluebirds, titmice and other kinds of birds. Even after beaver have abandoned a pond, their burrows become homes for other kinds of wildlife. Sometimes well-built beaver dams remain long after the beaver have left and the permanent pond continued to serve the needs of other species of animals. In places where the water is deep enough to meet the needs of beaver without their having to build dams, the beaver affect plants and other animals less than in areas where dams have to be built. The activities of beaver may in some such places be detrimental to man.