A couple of years ago my first flock of three chooks were killed by foxes. Two were taken and my favourite one beheaded and left behind. She used to hop up and sit next to me for talks and cuddles.
I took a break from chickens for a while then spent some of my tax return on a proper coop with a fox proof floor, to which I added further fox proofing. So far, so good.
The foxes live in the sand dunes and around the port where there are lots of different industries. So, although I'm surrounded by housing, there are ample hidey holes for foxes aroundabouts.