Is it legal to shoot/kill squirrels and birds with airguns?
It is illegal to shoot birds at all, with the exception of game birds and waterfowl during open seasons, certain nuisance birds such as crows under specific conditions, and Starlings, Rock Doves and English Sparrows. The latter three are not protected species and can be cleanly dispatched with an airgun. It is inhumane to shoot squirrels with an airgun. It is not a suitable weapon for an animal that size. It will kill them, but they will die a slow death. Legal questions are best answered by legal authorities. I suggest you check with your local wildlife management agencies.