Lay it down belly down, put your knee on its back and crush.
That's how I finish all my birds. Better than wringing neck, but you don't get to say you bit a ducks head.
X2 on big birds like geese, divers, sea ducks. Puddle ducks I squeeze the bird in one hand. Thumb and middle finger under the wings and compress the heart. 15 seconds and they are out.