The difference of attitude between North/South concerning squirrel still astounds me. They're still regulated as a game animal in ND. From my reading and correspondence, I believe the "damage clause" gets stretched a bit...
Anyways, field corn, peanuts in shell, bird seed etc: Bolt or single shot .22 and CCI CB ammo; less noise than an air rifle. Be very aware of your backstop. The bullets are 29grn and ricochets sound like a whistling firework. I sight dead on @20yds and "shade" high @35. Its best to have two scopes IMHE: ^^^^ TREE SQUIRREL vvv not ground. This ^^^^ is for gofers in the yard: