There are nearly three hundred species in the squirrel family, and some of them, called tree squirrels, are expert tree nest builders.
Some other species dig burrows and build nests there.
Tree squirrels belong to the genus Sciurus. Their nests are called dreys.
The common gray squirrel, Sciurus carolinensis, is a tree squirrel. Its natural habitat is the oak, hickory and walnut forest of the eastern United States.
It has been observed taking fine strips of bark to make its drey or to line dens in hollow trees.
Tree squirrels do not hibernate, though they may stay in their nests for days at a time in bad weather, huddled together for warmth.
The mother’s nest may be home to young squirrels even after they are weaned, and adult squirrels may share nests.