Woodpeckers excavate their own nest holes, it takes about two weeks before the cavities are ready for nesting. Most will use softwoods like aspens, others will use hardwood trees that have been affected by fungal disease, softening the wood. This is also the way the woodpeckers can carry the spores to other trees, helping them become home to future woodpeckers. Most woodpeckers will build a new nest every year, providing opportunities for various other birds and mammals to use the abandoned cavities as nests or dens. This American Marten was doing was using an old Pileated Woodpecker created cavity as a den over spring.
