Squirrels are very common in suburban, wooded areas. Never attempt to handle an adult squirrel as they are very excitable and handling causes intense stress. A stressed squirrel may bite or scratch. Many people believe that if you touch and handle a baby squirrel and the nest, the mother squirrel will not take the baby squirrels back. This is not true. Don't worry, the mother squirrel will always take her young back, so put the nest back into a tree as close to its original location as possible. Follow the link below to learn more about controlling squirrels in your yard.
http://www.nativeanimalrescue.org/?p=9