Very interesting topic!
Don't know if you're familiar with the Kilcher family, featured on the TV show, Alaska the Last Frontier, but they use a totally unique and pretty awesome method for harvesting thier poultry! I've only seen it done on a Turkey, but I'm sure you could work it on Ducks or Chickens as well.
Basically, they separate the selected bird from the rest of the flock and then put a large pile of food down on the ground. Naturally, the bird approaches the food pile and stands over it to begin eating. They give it a minute or two, for the bird to settle in and feel comfortable. When it is good and distracted, the executioner then approaches casually from behind, with a machete in hand. He stands behind or to the side of the feasting bird and then takes a golf swing with the knife, cleanly removing it's head before the bird even knows what happened! I know that sounds kinda brutal written out this way, but watching it on TV, the ease and grace of the process completely blew my husband and me away!