Being a farm boy, I'm not in to trapping a problem and releasing it for someone else to deal with. If people want pets, they need to keep them at home. Feral cats kill nesting songbirds in countless numbers every year. I hate em. I can tell you for certain that these work for what you're wanting, they are very very accurate, and are quiet and will cycle a semi automatic rifle because of the heavy bullet.

Aguila SSS Sniper Subsonic Ammo 22 Long Rifle 60 - UPC: 640420001364