I've killed a cheetah at very close range and a buff at 20 yards or so. the former was the best shot under duress i've ever made-they fly at you and there's not much light or warning.

as for crows-let me reiterate the Precharched Air Rifles in .22-25. daystate, air arms and evanix all make quiet and accurate carbines that will force you to use the heaviest ammo available to stay subsonic. a condor in .22 will do well over 1200fps with a 14.9grain pellet-i prefer eun-jins and jsb's.

anyhow, you can take a crow from 100 yards ethically and raccoons, possums, skunks and fisher cats and even coyotes at half that with a decent shot placement. they'll move less than 5 yards.