The American eastern gray squirrel, Sciurus carolinensis, is typical of tree squirrels. It is native to the forests of the eastern half of the United States. Gray squirrels have many color variations. They normally nest in tree hollows, and may construct leaf nests which are used principally as feeding shelters. They may breed in midwinter and again in late spring. Tree and ground squirrels typically are diurnal. Flying squirrels are nocturnal. Squirrels generally eat vegetation, seeds, nuts, berries, fruits, and insects.