Don't know where you live, but mustelids - weasels, mink, martens, fishers, etc. - attack poultry by the neck. I've been having huge problems with minks, and every single bird has had neck injuries, some with their heads bitten completely off.
A few weeks ago, a mink killed 16 of our ducks in one night, and injured all ten of the survivors. He came back a couple nights later and I killed him. Biggest one I've ever seen.
A few nights ago, I heard a commotion and went outside to see another mink killing a drake. I shot him and drew...
Update: it was indeed a mink. He came back for seconds and I caught him.
Also, I got my favorite drake back. A neighbor down the street told me there was an injured "Canada goose" under his deck. I went and looked, and sure enough. He’s pretty beat up and he was very hungry and thirsty, but...
Update. Big massacre last night. 11 ducks missing, 6 dead with injuries to their necks.
There are ten survivors, and every single one has an injury to the back of its neck. I'll be surprised if all of them recover, a couple are in pretty bad shape.
Three of the dead ones were stuck in chain...
Just found another dead Muscovy. The head and neck were missing, and everything else was pretty much just a skeleton, eaten except for the wings and feet.
A "bibbed" blue, because of the white on his chest? Looks like his flight feathers are coming in white, too. His head is darker than his body. He came with two lavender and and several black siblings.