This is good advice on removing possible hiding spots and food sources. I do suggest a metal bin would be better than a plastic, because if rats can chew through 2x4s and even concrete, I think they can chew through plastic.Try the following: 1) Mix baking soda with cornmeal or cake mix (50/50). Place in containers that will keep the contents dry (and out of reach of the chickens). Rats can’t fart and burp like other mammals, resulting in rats that explode from the inside. Predators won”t be poisoned when they eat them. My cat will offer my silkies dead mice that he finds in my yard. 2) Depending on the size of the rats, chickens will hunt them and eat them whole. This act would be a great video to show your neighbors. 3) Store your chicken feed in big plastic or metal containers. It should be noted that food from any pet will be a draw. 4) Cut tree limbs and clear any vines that rats can access for travel and housing. 5) Place all vegetables and fruit grown in the yard behind cages. 6) Bring home chicken friendly barn cats that love to hunt rats and mice.
Study your yard to determine sources of food, housing, and transportation for the rats. Tree limbs in my yard touched the field behind my house to create an entry for a rat problem in my yard. They chewed through the bags of feed in my garage and yard. Everything is now in big plastic bins.
What I suggest, while the flock is away, get some one-bite rat poison and kill off all the rats before they get back. I don't know where the rat holes are, but with the rats I've dealt with, they were living under the chicken coop (which had the grain stored in a room in the same barn). I had a winter run that nothing but the rats were going into (it was on their trail to the grain room) and I would screw a One-Bite block of poison on their trail in there. Within a few days, the rats were either dead, or too sick to return for more. (I could tell the rats were gone by them no longer eating the poison.) With this setup, the rats had no reason to go to the outside world, so being exposed to predators (such as the strays and neighbor's cats) never happened.
This has worked well for me, though I don't trust it to keep the rats away forever. Between my neighborhood's dumpsters and trash, the rats do return, and as soon as I discover them, I'll set the poison back out again.