Darn fox, if they weren't just so beautiful. Do you have a live trap or access to one? Surely where there is one fox, there are more, and the word is out amongst them. Plus once they make a kill, they'll be back for more, it is a free fox buffet after all. But you know all this already. And yes, do be careful, rabies are out there, and the fox tend to hunt during the day. Maybe scattering your free range times will help confuse them a bit, that seemed to help us, eventually they gave up, but not before they had taken about 10, that was in spring tho when they have their litters, and it was consistently every other day, at the same time, between 11AM and 1PM. We left the chickens in the pen for about a week (broke my heart) and it stopped altogether. Have seen a fox run right thru property with a big chicken in its jaws from a neighbor's place a couple miles away, but he's got well over 100 free rangers and he doesn't seem to mind too much if one or two go missing. Wish I had that attitude, but we're down to 10 right now and can't afford a loss. Trapping/hunting fox season starts Oct 15, but if you have a nuisance animal on your property, it's a different story. Hopefully we'll have a hard winter and get the population down a bit. Also, if you know a trapper, he/she would probably love to trap for you, fur prices are at an all time high.
I did let the chickens out between noon and 5 p.m. They don't exactly free-range, so much as roam around in a fenced off area that is not fox-proof. We don't let them out unless we are home, but we certainly aren't right out there with them, so we take a chance.
If we start losing them, I'll stop letting them out, I suppose. If it comes to that, we can always move the hoop house more frequently, although moving it is a big project. There is hardware cloth all around the outside, weighted with rocks and secured with earth staples, so all that must be taken up, and then we have a system of putting rollers underneath and pulling with the tractor. The tractor is actually gone for major repairs at the moment.
I haven't seen my neighbor's chicken pen, but I kind of doubt they are as high-security as we are. Plus they are likely to shoot or trap predators, so that may help us. We've had great luck here so far (no losses), but I know that can't continue forever.