With doves, quail and woodcock I hang the bird by the head between my first two fingers and, with my thumb, press it's head sideways until the neck breaks. Flapping ensues but only lasts a few seconds, then life is gone. The flapping is an involuntary reaction, the same every time.
With ducks I put it's neck in my mouth and bite as hard as I can to break the neck bones and sever the spinal cord. They make a tool that accomplishes the same thing. I seldom have to finish off a duck so have never bought the tool. I'd either forget and leave it home, or lose it, anyway. I'm a minimalist when it comes to hunting. I don't pack much paraphernalia in my "kit".
