I have rats and then some. It seems that every once in a while, one will turn into a blood thirsty killer and if the chicks are small enough, they will drag them off and eat them.
I have an old door laying around in my barn, took the door to a corner of the building, lay the door on it's hinges and leaned the door against the two walls of the corner so it created a private area that the rats could get in and the chickens could not. I put a nice huge bag of poison rat blocks behind that door and let them eat at will. You may need to place a piece of plywood over the top area of the door block so the chickens can't hop over. My barn has a shelf along the back wall so mine was covered.
Some of the poisons they would just gobble up and you would never see a body, other stuff they would eat and it looked like a battlefield. The more you spend, it seems the better the results.
Okay, this is nasty, NASTY, nasty, and totally inhumane... but non-toxic... when i was a kid, we had chickens, and got wicked rats in the henhouse, and they would eat the eggs... anyway, my parents put out powdered mashed potatoes... the ones in the box. Anyway, the rats eat it, and then it swells in their stomach, and bursts them.... one of them got stuck, dead, midway through the chickenwire... totally gross... but it killed them!
I had one rat a couple of years ago. I kept losing my chicks and poults. One 4th of July I noticed a small hole dug under my chicken house which had a floor of laid plywood over half way. I had my son put a smoke bomb in the hole. Smoke came out of several places, including under the plywood. I pried the wood up and there was a series of tunnels and remains everywhere. The rat came running out and my rat terrier caught and killed it. That's why I now have a dirt floor. So to answer your question, rats will kill birds. I keep poison in small crawl spaces that chciks cannot get into. No more rats.
I also suggest a good cat. I have one who leaves my chickens alone.. occasionally he will try to play with them and create chaos in the coop.. but he has learned after run ins with rooster that chickens are not for him to eat.. but the rats he catches are!!! I am always leary about poison/baits and will try other measures due to risks associated with poison including the poisoned carcass being consumed elsewhere.. a good measure is keeping area clean and tidy- don't spill bunches of food around.. and I also have my coops built up off the ground so that cat is actually able to go under the coop.. deters the rats from at least living/tunneling underneath..
I started seeing rats about and hearing them so I knew I had a problem. I built little bait boxes where I would put that chunk poison bait-- the box would have a hole big enough for a rat to get in but, the chickens couldn't get to the bait. I also put bait in my attic. Later, I found two dead rats in my basement.
A couple of years ago, I had a one-eyed, old, stray tomcat show up & I started feeding him. It turned out the only animal he'll kill is a rat so I started feeding him religiously & now call him my cat. I have not had to use anymore rat poison since he showed up-- I have not seen another rat or signs of one.
Not all cats are rat killers/hunters-- but if you find one, they're worth gold; just about all cats will kill mice, chipmunks & wild birds though but only a few will actually hunt & kill rats.
Okay, this is nasty, NASTY, nasty, and totally inhumane... but non-toxic... when i was a kid, we had chickens, and got wicked rats in the henhouse, and they would eat the eggs... anyway, my parents put out powdered mashed potatoes... the ones in the box. Anyway, the rats eat it, and then it swells in their stomach, and bursts them.... one of them got stuck, dead, midway through the chickenwire... totally gross... but it killed them!
I may have to try this... i have tried the rat blocks... i put it out and they take the whole block? and i still have rats.... good thing they don't eat the eggs... i think anyways?