Another thing to keep in mind (and it may not work, but I'd try it) is that ducks will allow themselves to be herded quite easily. Now my own ducks are slowly trained as ducklings to learn to respond to my body language communications - I lean a little or put a hand out and wiggle my fingers and they know where to move. Mostly they move away from "pressure" and you have to learn how close to come and how slowly to move not to panic them. Two or three people could pretty easily guide ducklings into a wide opening, IF they were experienced at moving ducks. Move very slowly, approach only until you get movement form the ducklings, then wait until they stop, watch to see how they respond. At the range where they start to respond to you try moving an arm out slowly, then maybe wiggling your fingers. They move away from movement. They respond to the pressure of your "eye" like they would to a herding dog too, kinda hard to explain, but when I pick one out of the flock to catch I start watching her, the others move away from her and she knows who I want. I enjoy this communication with my ducks. I can see why people use Runner ducks to train herding puppies. BTW, those do look very much like Runner ducks. I hope you can find a way to help them.