Fox attack

we had a rogue fox last year, i think he must have been dispatched one way or another as he hasn't been back, a few weeks ago the local hunt drew the wood next to our farm and foxes spilled out all over, hounds were off in every direction, last week someone thoughtfully left 4 dead foxes at our farm gate, they had all been shot, my point being my birds free range the farm, none are penned up, yet i haven't lost one to a fox since last june, i expected to lose the odd one and just hoped it wouldn't be a favourite, we have about 80 birds of various breeds and sizes, and they are everywhere, i don't really understand how none of them have been taken.