Last year this happened to one of our Hens in the run. I found her under a tree in the run. We do not have possums or coons. Been here 10 years. The one I found was missing the whole neck and head but, not any coons or possum. One critter was feed on ours at 2 pm in the afternoon. I count birds through out the day in the run. If all are not present I check the coop asap. The one feeding on her was a different type of squirrel last year. This one was not scared of people like the other squirrel we have had over the years. I am out on our deck watching most of the day and evening. I also can see our girls through our sliding door so I'm always watching. This is the only one over the years. This happened around June last year. She wasn't even a year old yet. She was one of our hatch girls in 2020.