Habitat
Prefers deciduous and mixed forests, particularly beech- maple, oak-hickory and poplar. Also occurs in old orchards. In New Hampshire, preferentially used areas with large shagbark hickories and beeches; males tended to use areas with large oaks, females tended to use areas with abundant snags (Fridell and Litvaitis 1991). Favors small, abandoned woodpecker holes for den sites; also uses nest boxes and abandoned bird and squirrel nests outside tree cavities.
Ecology
Highly sociable, particularly in winter, when communal nesting peaks; communal nesting aggregations occur in both northern and southern populations (Layne and Raymond, 1994, J. Mamm. 75:110-120).
Population density was estimated at 31-38/ha in southeastern Virginia (Sawyer and Rose 1985), 10-14/ha in Maryland, 1.5-2.5/ha in Michigan-Massachusetts (see Layne and Raymond). May be ousted from cavities by some large cavity-nesting birds; may kill or oust some small cavity-nesting birds.
Reproduction
Gestation lasts about 40 days. Births peak April-May and late summer in north, late February-March and September-October in south. Litter size usually is about 2-3 in south, 3-4 in north. Young first breed in spring after birth in north, may breed late in 1st summer in south. Two distinct breeding periods in New Hampshire, February-March and June-July; two litters per year (Stapp and Mautz 1991).