one thing i found out is a wild fox out in the country ( not urban ) have a set feeding area , this will take around 7-14 days for the fox to go around , it might take one chicken and move on but will know it can get another there when its back to that area . best thing to do it try shooting it or set a live trap ( if you don,t want to wait up all night) bait the trap and follow live trapping rules ( make sure there is food and water in the trap and check every 12 hours) once you have it in a trap then shoot it . remember the fox is on the pest list and can be disposed of , but has to be done humanly . also remember that as it is a pest it is illegal to release it on someones property without consent ( and would you give consent to someone releasing pests on your ground ?)