Eastern grey squirrels typically are grey but have some variation in color. Gray squirrels often are found in great numbers in cities, especially in and around parks. The presence of mature hardwoods often is important to both species. Typically, they feed on mast (wild tree fruits and nuts) in fall and early winter. Acorns, hickory nuts, walnuts, favorite wild foods but if there is bird seed around, they will stop at nothing for that delicacy. It may not seem like it but squirrels are one of the most dangerous pests as they chew on electrical lines, leading to fires. If left long enough, their gnawing can weaken rafters.  Squirrels, being rodents, are known for their gnawing. The size of holes made by squirrels are usually the size of a baseball. Through those holes they will enter buildings and build nests in attics. They may chew holes through air duct work in the attic too.