If you have trees, you'll have squirrels. On a typical city block, you will normally have about 5 squirrels for every 3 yards, (depending on size of yard). If you get rid of your squirrels, more will move in.

Instead of trying to eradicate them, it's best to focus on your home, making sure that you have no vulnerable spots where squirrels can get into your attic, for example. You might want to consider trimming back any tree branches that are hanging over your roof, etc.

If squirrels are coming to your bird feeders, you can get squirrel baffles, or a feeder that closes when a squirrel puts his weight on it, such as a Squirrel Buster. These can be found in specialty shops that sell bird feeders and seed, (and probably also online).