Can I get back to you tomorrow with an answer to that question :-)? Seriously, I don't have enough information to answer that right now, but if the weather cooperates tomorrow, I can do some chrony work and have an answer.
The questions really are, how much energy is retained at 70 yards? And how much energy does it take to be certain of a clean kill on a crow? I wish Jeff, aka Longislandhunter, were online right now. He's the hunting expert, and probably has a much better idea of how tough a target a crow is. But I CAN do some chrony testing at muzzle and down range, and I have software that will allow me to extrapolate retained energy at various ranges. So like I said, if the weather cooperates tomorrow, I'll give it a shot. Or should I say, several shots :-)?
One important variable is going to be pellets, and right now, JSB Predators seem to be the top of the heap in hunting pellets. I have some, so will use those and Superdomes for testing. Both shoot well in my 350. I have a pretty good selection of pellets on hand, so if there's something else you'd prefer, let me know. This sounds like fun. Too bad I don't have any .177 Predators, it would be interesting to do the same test with my CFX.
Dave