I think that is the only answer is to pen them up at night. I have several of the dog kennels that we keep some of them in now. Even the dog kenels have to be re-wired or a racoon can pull them thru the wire. I have a huge number of Sebastopols and a couple of buildings I can cram them into at night. If the electric fence doesn't stop the problem. The BYC person that said he uses a night camera to see what was killing his stock will get more info to us on purchasing the camera.
What are the signs when a fox has been the preditor? I suppose a fox carries its prey off but don't know that for sure.
By the way, the fenced pasture that my Sebs. were getting killed in, has a large pond I would think the geese would get on if they saw a preditor in the yard. They sure know enough to head for the pond when the see me coming with a camera.