I have a friend who went out for not even 2 hours and when she and her husband returned home something had killed all her adult ducks and adult chickens. Whatever it was didn't eat any of them. She got lucky because there happened to be a nest of duck eggs that just hatched in a hidden place and also one of her hens was sitting on a nest of chicken eggs which hatched later that evening even though the hen got killed. It didn't lessen the loss of her adult birds. I know where we live there is a mountain lion in the area and there are coyotes (which is what she thinks got her flock). I don't know what other predators lives area here in a town near Edwards AFB.