I think it was a bird of prey. I am having trouble with this right now too. It's the bird without the head that clues me in. A couple years ago I had a hen that would fly up to the top of the apple tree and then give a speech. One day an eagle tried to pluck her off the tree by lifting her by the head. This is gruesome but what happens when they do that is the body is too heavy and the head pops off and the eagle is left with just a head in his claws. I found my girl shortly after this happened; she was still warm. I deprived the eagle of his prey by bagging her up and disposing of her. This last week I lost a chicken to another eagle and I have an injured girl in sick bay. If your chickens can fly out of the run, they may have flown to safety and that's why you found them elsewhere. I don't know where you are, but where I am the salmon aren't running like normal and the eagles depend on them. They are desperate to feed their own young, so they are going after our chickens. I have now set up obstacles so my girls will be safe. I hope. I can't close the top of my chicken run because it's my little orchard, so I set up tomato cages upside down, spikes up everywhere. The chickens can still range wherever they want but the eagles don't have a landing spot. Remember they have to swoop and grab. They cannot outrun a chicken on the ground. I feel your pain. The one I lost this week was one of my original hens. So sweet and lovable. The one in sick bay was also one of my originals. She is not doing well atm. Heart breaking.