Well that wasn't pleasant for any involved.To be clear it was a duckling, about 5 weeks. Idk If ducks have stronger necks but it did not cut the head off. Instead it forced the lopers apart sideways. The loper blades are tall and strong in one dimention but thin side to side. So the blades bent out with the neck between the blades. I loped 3 times, still not dead so i loped again and twisted to break the neck. It was not a humane death in any fashion. I was very surprised it did not work. Pvc cutters are designed differently and may work. Photo so you can understand what I'm talking about.

I have had that happen to branches with dull loppers