Perhaps I don't know the proper "technique", but my experience with trying to snap a chicken's neck went horribly wrong, and I felt bad for making it suffer for so long. She was an egg eater, and I caught her in the act of breaking them open. Anyway, the neck would not snap, but after she was strangled nearly to death, I used the shovel.
Chickens necks do not snap very easily, imho. A duck would probably be even harder.
That sausage looks good. I see that your recipe doesn't have any added fat; do you think it has enough with just the duck meat? I realize "enough" fat is a relative term but I really dislike this new fangled lean sausage. I keep meaning to try some with the semi-tame resident Canadian geese we have.
What about using very sharp pruning shears to cut the head right off? Slitting the throat would be to gory for me and knowing my bad aim, I don't think using an axe would end well.
Those sausages look absolutely delicious
I hate to have to kill the poor duck, but at least I've got duck sausages to look forward to