I know a Lot of ye here love ye chickens. And, who better to ask about what caused the carnage below, please?

OP tells me there was No 'musky' odour. And that 'weasels' are few and far between, around them.

They're ready to go to war on ..... Well, just about Everything, basically. Specifically naming fox, (Feral) cat, 'coon and grinner. I've no personal experience of the last two. But, I told the OP I knew Just the people to ask

Photo shown with their permission:




Thanks.

Rats

X2 my first thought as well

Yup

Sad deal...Rats are a real pain

X 3 rats

rats

Before signing on to the rat theory, how many baby chicks and what age? Days? Weeks? All at once? How were they killed? Bite marks? Heads ripped off? Eaten? Any evidence of rats as in tunnels, etc, with a baby chick pulled down the tunnel? Rat droppings?

In the absence of bite marks, etc, Id also be looking at contaminated feed, water or if very young, did they freeze to death?

There went some ones 401k.

HayDay; Owner said he never sees rats. Mentioned some sort of what he called gray 'Field Mice' (He wasn't certain himself what they were. I wouldn't have a clue, obviously)

I copied the photo down and blew it up to 160%. It's an absolute massacre. Really no particular 'trade mark' evidenced. Disembowelment. Dismemberment. Some appearing to have been just bitten and left. There really is something for everyone amongst that lot. And it was enjoying itself. Nothing even looks Partially eaten.

He mentioned that he's inundated with squirrels and raccoons. But, that he always has been. And he's been raising chickens there for years.

Made me wonder if it was something passing through. I wondered about feral / bob cat. Or, maybe that Tasmanian Devil, from the cartoons. Blow the shot up and it really looks like He's blown through there.

You can have rats and not see them for a while I noticed holes chewed through my coop walls long before seeing any actual rats.

Sounds like weasel to me. A stoat is a weasel by a different name.

Pattern of the kill is total massacre.........normally bite the back of the head at base of spine......sever it there and move on to the next one. Will keep going to nothing left to kill. They normally go after rats and mice.......so those attract them, but they are equal opportunity killers, so just set in the birds instead.

One more long shot is somebody's little dog......rat terrier, etc, Got in building.....then in what looks like a livestock water tank......killed all the birds, then jumped out and left. Same pattern as a big dog and grown chickens.......smaller scale.

I have seen cats do that as well and not just feral hungry cats either but we’ll fed ones, get in a pen and just keep killing until there’s nothing left alive, some ripped up some just killed and moved on to the next and total slaughter throughout

Several years ago I lost a 100 baby ducks to a cat and it looked a lot like that, found the culprit in the pen and it didn’t make it out, was the neighbors cat

Watched a mink in the UP one summer while floating a river hunting off a log on the bank going into the river, it wound dive into the water and come up with a smaller sunfish then bit it and put it down and went for another.