We have ducks. Several weeks ago I noticed a few burrows going down under the pond liner that we have, and a few weeks ago, I flooded them thoroughly enough to drive a huge fat momma rat with swollen udders out of the pen where my malamute/pit mix promptly caught, killed, then didn't know what to do with it. I collected it and trashed it. Thinking that I had killed any potential young by flooding the tunnel, I left it at that. A week ago, I caught & killed one, and the dog caught & killed another. One got away. A couple days ago, I flushed the one that got away out, and the dog killed it as well. There was at least one more that I saw scurrying around that we have not yet caught/killed. I want them gone. I have done the 5 gallon bucket feeder and have it hanging. The ducks are just messy with how they eat and some invariably gets dropped on the ground. Removing the food source entirely is not an option. I am hesitant to use poison, as the ducks are curious, clever and will eat anything. Also, if the dog catches one and manages to eat it, I don't want him to be poisoned. I have seen a 5 gallon bucket method, but I can't see the ducks not trying to perch on it. Live traps? Liquid nitrogen? An army of trained wasps? I assume that since it's such a sweet deal for the rats, even if I kill the existing ones, I expect that new ones would want to move in. Can I start taping razor blades to the ducks toes?
Although razor blades seem ideal here I would trap them...all the time. My boyfriends father sets up live traps and puts metal crates around them to keep his dog out and then when he catches something unwanted he drowns them or gasses them. I know it sounds kind of cruel, but at the same time they're disease ridden and it's much safer to just eliminate them. Unfortunately it's a continuous process since the supply of vermin is unending.
Make a bucket trap. For mice and small rats you can use a 5 gallon bucket but for bigger rats you may want to you a 35 gallon trash can. Just fill bucket/trash can half way with water, have a ramp from the ground to the rim of the bucket/trash can then have a can with a wire running through it and attached to each side of the bucket/trash can and the can must spin. You can bate the top of the can with peanut butter. Not my picture.