Birds cannot sweat — learn to read the panting
A chicken or duck has no sweat glands; it cools itself by panting, holding its wings away from its body, and losing heat through its comb, wattles, and legs. Occasional panting on a hot afternoon is normal work. The picture that should worry you is a bird panting constantly with its beak wide open, wings drooped and held out, comb gone pale, unwilling to move or eat. That bird is losing the battle with the heat, and heavy breeds, older birds, and any bird already off colour get there first.
Shade and water, arranged for the worst hour
Shade has to be planned for the whole arc of the day, not the morning: a run that is shady at breakfast can be a sun trap by mid-afternoon, which is the dangerous window. A tarpaulin, a sheet of shade cloth, or moving the run against a hedge gives cover that lasts. Put water in several places so a timid hen is never bullied away from the only drinker, refresh it with cool water at midday, and set one shallow tray in the shade that hens can stand in — chickens cool noticeably through their feet. Frozen bottles of water laid in the coop and run give birds something cold to sit against.
The ducks' head-dipping rule
Ducks cope with heat better than chickens in one way — they love water — and worse in another: they must be able to dip their whole head. A duck keeps its eyes and nostrils clean and healthy by dunking, and a duck in heat stress will make straight for deep water. Give them a trough or a small pool deep enough for a full head dip, refreshed daily, set in the shade so the water itself stays cool. A duck who can bathe and dunk will come through weather that flattens the hens.
Coop air and the evening routine
A closed coop at midday can be the hottest place on the plot, so ventilation matters as much as shade: open every vent and pop-hole the coop has, and never shut birds inside during the heat of the day. Do catching, cleaning, and moving in the early morning, and skip handling entirely in the afternoon peak — being chased and held is hard, heating work for a bird already at its limit. Offer feed in the cooler hours, since digestion itself generates heat.
Heatstroke: act in this order
If a bird is limp, unresponsive, or has collapsed, act at once: move it into shade, stand it in cool — not icy — shallow water or drape a wet cloth over its body, and offer cool water to drink without forcing it. Keep it somewhere quiet and shaded to recover, and contact a vet or experienced poultry keeper promptly if it does not brighten quickly, because heatstroke damages organs beyond what the eye can judge. Whole-flock losses usually happen in a single bad hour, which is why the midday check is worth building into the day. For questions that arise at the run, with a panting bird in front of you, put a follow-up question to KinsLe's Kimmy; she answers using the KinsLe Answers library.