I believe but maybe wrong but isn't it illegal to kill songbirds? Poison millet will also
kill federally protected species and I don't believe anyone can recklessly set out poison
even on their own property. Rat poison is usually dyed a bright color and the boxes have
warning signs on them.
I would sue your neighbor through an attorney. Poisoning your food supply
is attempted murder. If you go to court and lose at least you got him on notice.
I would also setup some security cameras, take pictures of the injured and dead
chickens for evidence if you go to court. Its entirely...