Why dusk, specifically, is the killing hour
Foxes are crepuscular hunters: the half-light of evening is when they move, and it is also when hens are at their most obliging — drifting back toward the house, distracted, gathering near the pop-hole in a loose, vulnerable group. A fox that has watched your garden for a few evenings knows the timetable better than you do. It knows when the flock comes in, which hen lags behind, and how long after sunset the door usually closes. Everything in fox-proofing at dusk is about breaking that pattern: being earlier than the fox expects, and leaving it nothing to work with on the evenings you cannot be early.
Win the evening with the shut-in routine
Make the pop-hole closing a fixture, not a chore that floats: shut it as the light begins to go, which in midwinter can mean mid-afternoon, and count the birds in as you close it, because a hen missing at dusk is a hen in trouble tonight, not a mystery for the morning. Hens put themselves to roost as darkness falls, so the routine mostly asks you to be prompt, not heroic. An automatic door is a useful servant here but a bad master — batteries die, tracks jam with litter, and a door that closed on six of your seven hens has done the fox's work for it. However it closes, someone should confirm the flock is complete behind it.
Harden the run for the hours they are still out
The run earns its keep in the last hour of light, when birds are in it but the day is not done. Foxes dig, so bury or lay a mesh skirt around the base; foxes climb and jump, so cover the top with mesh or netting rather than relying on fence height; and foxes learn latches, so use bolts that need two movements to open. Electric poultry netting gives a movable extra line for free-ranging areas, provided the energiser is on and the bottom line is not shorted out by long grass. Walk the run's edges weekly — a shallow scrape at one corner is a fox's notebook entry, and the night it comes back with intent is not the night to discover it.
Make the garden itself less inviting
A fox prefers to approach unseen, so strip away its cover near the run: keep grass short along the fence line, move woodpiles and dense shrubs back from the boundary, and do not let windfall fruit, spilled feed or open compost sit near the housing scenting the evening air. Feed stores should be lidded and rat-proof as well as fox-proof, because a garden that feeds a fox nightly will keep one nightly. A motion-activated light over the run can unsettle a cautious fox and alert you, though it is a seasoning on the routine, not a substitute for the shut door.
After a near miss, change something that same night
A fox that has almost succeeded will return, usually within days and usually bolder. Keep the flock confined to the secure run for a while, reinforce whatever it tested, and shift the free-ranging hours. If a bird is injured, even with punctures that look minor, she needs prompt veterinary attention, because fox bites seed infection deep under unremarkable-looking skin. And because a hunting fox ranges across many gardens in one night, a sighting shared through KinsLe's Circle of Love warns every keeper nearby to shut in early and check their defences — the fox that emptied a coop two streets away is already trotting toward yours.