When I first got chickens, (Me being inexperienced and all) I put them in a triangular coop and at night I would put them up in the roost area of it. One day I came down to the yard and they were all gone. There were no feathers or carcasses and barely any blood. All that was there was a shallow hole, maybe 4 inches deep and 7 across. Note- We live on top of a wooded hill, and at the bottom of that there is a swampy pond if that helps.

If you have a game camera put it up because more than likely it will be back then you will know what you are dealing with. I would suspect first a fox. Many predators are diggers. I lost several birds to a bobcat that dug under a fence and a fox that dug under a gate. I now have electric wire around my pens and coops, concrete under the gates and netting covering all of the pens because of an owl that got in and killed some birds. I put a game camera up and did catch the predators.
