I started out small game hunting at a young age and continue the tradition, but I don't think I've ever thought to try bow hunting squirrel. Watch this video below and see it's possible.
Small game heads can be found for under 25 bucks. So, if you have a bow and some practice arrows around, it's pretty cheap to get started. Personally, I can't think of a better way to practice with my bow. You also get a few squirrels out of the deal as well. It might be worthwhile to keep a small game head in your quiver just in case. As the video states, the heads are large compared to the squirrels, so as long as you make contact with the body, you have a bushy tail dinner.