Get them shut in well before the first bang
Chickens put themselves to bed at dusk, which does most of your work for you — the preparation is to bring that routine forward on fireworks nights so the flock is settled well before any display starts. Feed a little earlier, let them file in as usual, and count heads on the perch rather than assuming everyone came home. Then latch the door as if a fox were doing the inspection, because that is closer to the truth than it sounds: a startled hen flinging herself at a poorly fitted pop-hole door can burst it open, and a bird loose in the dark with fireworks overhead is the scenario you are actually preparing against.
Make the coop feel solid and boring
Inside, the aim is a space where a frightened flutter does no damage. Put down deeper bedding than usual so a bird coming off the perch in a panic lands softly, take out anything loose or sharp-edged that a flapping hen could crash into, and check for gaps at floor level where a scrambling bird could wedge herself. If your coop has a window that faces a regular display site, covering it for the evening softens the flashes; the bangs still arrive, but chickens read the night through light as much as sound, and a coop that stays dark and still reads as safety to a roosting bird.
Keep the evening routine exactly the same
Do your jobs in the same order, at the same unhurried pace, with the same feed call you use every night. Chickens take their cues from the flock's behaviour and from yours, and a keeper rushing, catching birds up for inspection or fussing around the coop with a torch at bedtime tells the flock there is something to fear before a single firework goes off. Handle nobody that night unless you must. A hen's best fireworks night is an aggressively ordinary one that happens to be louder outside the walls.
Check the flock once things go quiet
When the displays are over, do a quiet torch check: every hen accounted for, nobody on the floor injured from a panicked flutter, nobody missing. A bird with a torn wing or a leg hurt in a scramble needs attention that night rather than at morning inspection, and a hen who is simply wedged or hiding needs finding before she spends the night cold and exposed. If one is missing entirely, do not chase around in the dark — a frightened chicken shelters low and silent close to home, and the first-light check of hedges, sheds and undergrowth around the coop finds her far more reliably.
Let your neighbours be extra eyes
Tell the neighbours around you that hens live at your address and it is fireworks season; most people are glad to know, and a hen over a garden fence is returned in minutes when the finder knows whose she is. That local awareness is exactly what KinsLe's Circle of Love builds — free accounts connecting nearby pet lovers into a network that looks out for each other's animals — so if a hen does slip out on a loud night, more local people already know she exists, where she belongs, and that she needs a hand getting home.