I do it to end the life of a wounded but not yet dead bird. And, of course, I don't do it with my teeth.
But to a bird, a beheading is a beheading and I don't think a quail would agree that it's fine just because I was hunting it, as opposed to grabbing it off someone's shoulder as a drunken prank.
We are going to have to agree to disagree on this one. Hunting dove and quail legally and doing all that entails and grabbing a pet parrot off a guys shoulder in a bar then biting it's head off because the biter is so drunk he doesn't even remember doing it are totally different things.