Always upsetting when they've been, do you have a dog you can leave loose during the day?
Urban foxes don't seem too bothered about waiting till dark, esp. if someone is feeding them.
We had one about 9.30 in the morning, found some poor hens that had tried to get into the dead grass at the bottom of the fence, bitten on their backs, but presume died of shock. The one that wiped us out was 8.30pm in June, I'd heard them skwarking (?), but just thought they were fratching, cockerel even came looking for me but I put him back over the fence. (He did survive, and one that was caged because she was broody). Everything else, including my gorgeous little call ducks gone. I was working on some fencing less than 50 metres away. Stupid me, I can never forgive myself.
Damn stupid rescue people.