I hate foxes and that's just how quickly you can lose all your poultry.
Most people don't realise just how small a gap a fox can get through. I've dug a afox out of a 4" drain pipe. They're very cat like and basically, they can get their body through wherever they can fit their head.
I'll get Karen to put this post on the poultry section along with a warning, as soon as Kaz comes home from attending the knitting group at the local pub.