This situation actually reminds me of a situation a school friend was in when he owned a flat with a little garden over here.
His neighbour would let their cats ***all over his garden, he even caught them watching the cats crap and then calling them inside!
So he thought he would make the cats a little "poorly" and crap all over the neighbours house.
He spoke to a friend who worked for pest control and got hold of some poison, but was warned that this stuff was SERIOUS stuff. The measure used in rat poison is 1/100 of this stuff or something stupid.
So he put a sprinkling of this on some cat food (/sigh..... yes..... a sprinkling).
The Cats dropped INSTANTLY dead upon taking one mouthfull and foamed all over the place.
Horrible I know......
BUT
Next day he comes downstairs after a bit of rain in the night (after removing the incriminating cats the night before with mounting fear of what he just done) and sees a dead fox under the tree and 4 dead birds that had eaten an apple on the floor from the tree. The patch he put this sprinkling on became a death zone for about 2 months.