I don't know how much they eat, but any amount is going to start the gas buildup inside them that they can't expel. I don't see why you couldn't mix it with peanut butter and use it that way.
If you have any pets, whilst this isn't poison to them, I'd keep it out of their reach as otherwise...
So sorry. I guess this means war. I would find another place to put your chicks and try this again. They preferred fresh meat to the "food," and with no fresh meat, they have no choice. They will eat it.
I'd assume a shrew would eat it, and it's extremely cheap to just try it.
If you think the ducks would get into that bucket idea, just put it in a bowl and set it inside a cage that varments could get in, but your ducks can't.
I hope it works. Please let us know.
Once you get rid of that nest under your coop, you could bury the hardware cloth about 6" around your coop and attach it to your coop. I'd pile rocks around it then too. (We happen to have lots of them, but if you don't, perhaps you have bricks or...
It looks light enough that you could empty it out, tip it over, then run your hardware cloth all over the bottom and up the sides. Steel wool can fill holes.
Try killing them. Mix equal parts of corn meal and baking soda. Jiff cornmeal mix is cheap and works well as it's got a little sugar...