There will be plenty of folks telling you to kill the fox. My argument is that only takes care of the predator you see. Also, you get rid of one and another one moves in. So lots of killing wildlife that does not solve the problem - basically, that your birds are unprotected.
Some idiot dropped 3 roosters of at my house a few weeks ago. Unprotected by coops and runs, and not catchable, they lasted 3 days before vanishing - dinner for one of the many predators that surround my property. I have never lost one of my own birds, with the exception of a wildish little hen that would not go in the pen one night after free ranging for an hour.
Build a sturdy, predator-proof run to keep your chickens in while you can not be with them.
