Is it a grey fox or a red fox. Greys are hard to catch in a live trap, Reds are almost impossible. They are very claustrophobic. Once it is conditioned to an easy meal, It will not quit until the meal ticket is either inaccessable or all gone.
As much as we all love our chickens, I have a soft spot for foxes. I do trap and hunt them in season, but I would never condone eliminating or relocating one prior to September and condemning their pups to a slow starving death. If you are successful in trapping it and it's a male, no problem. If it's a female you may need to secure your birds until it's humane to move or dispatch your killer. Foxes aren't evil, they're just doing what foxes do. Also remember that if you relocate a poultry killer, you are just passing your problem on to someone else with chickens.
If you have a red fox, your best bet might be adding a rescue border collie to your operation. Most will adopt all your livestock as their own once you train away the initial BIRD-CHASE-EAT instinct. Our golden retriever pup is coming along nicely. He still mouths the birds a bit but will not bite them. Also likes to help herd them into the barn and he's getting really good at finding and flushing the birds that try to roost in unauthorized locations at sundown. He's learned not to chase or jump at the flush. Good pheasant training. Even the scent of a dog, especially a male, around your property will help somewhat in deterring canine predators.
If you want to trap a red fox, you will almost certainly have to go to a #2 coilspring foothold in a dirthole or flat set. TThis trap will also hold a coon or even a Coyote if firmly staked and checked regularly. They make a rubber jawed version that will require some advanced animal handling skills if you want to live trap and relocate. Bait with a commercial canine lure.
