Treat him as the tropical bird he is
A hill mynah needs genuine tropical warmth in cold winter weather, not merely a room that feels comfortable to people in jumpers. Hill mynahs come from warm, humid Asian forests and have no underdown worth the name, so a chilly hallway or a cage near a window can chill one quickly. Keep his cage in the most evenly heated room in the house, away from exterior doors that spill cold air across the floor each time they open. His normal chatter and bouncing activity are your thermometer: a mynah still whistling and hopping between perches is coping, while a silent one is telling you something is wrong.
Fight the dryness of heated air as well as the cold
A hill mynah breathes comfortably in winter when the air stays moist, so run a clean humidifier near, not aimed at, his cage, or set him where daily household steam drifts without blasting him. Central heating can drop indoor humidity hard, and dry air irritates a mynah's respiratory system and dulls his glossy plumage. Offer a shallow bath of lukewarm water daily; mynahs bathe enthusiastically and a bird that bathes and shakes off happily is regulating himself well. Let him dry fully in the warm room before evening, and never put a damp mynah under a night cover in a cooling house.
Manage soft food carefully in a cold house
A hill mynah's winter diet needs tighter handling, because his fruit, soaked pellets, and soft foods go cold, limp, and then sour in a chilly cage corner. Serve smaller portions more often, set the dish where the room's warmth reaches it, and remove uneaten soft food within a few hours rather than leaving it to be picked at all day. A cold snap is not the moment to overhaul his menu; keep the familiar fruits he eats eagerly so his energy intake holds steady. Check his water drinker morning and evening too, especially if his room cools overnight, and refresh it with comfortably cool, not warm-from-the-tap, water.
Keep his world bright and occupied indoors
A hill mynah stays healthy through winter when short, dark days do not shrink his activity, so position his cage for the best natural light the warm room offers without placing him against cold glass. He is an intelligent, social bird who mimics household sounds; a silent, isolated back room that happens to be warm trades one problem for another. Keep his routine of conversation, out-of-cage time in the heated room, and evening cover at consistent times. If he flies free indoors, close off routes to kitchens and fireplaces, since a bird seeking warmth may land somewhere dangerous.
Act fast on the quiet, fluffed mynah
A hill mynah needs a veterinarian promptly when a cold spell leaves him fluffed and silent beyond a brief nap, because this conspicuous, noisy species does not hide decline subtly for long. Open-mouth breathing, tail bobbing, discharge around the nostrils, or fruit refused for a full day all justify a same-day call. Warm his travel cage before the journey and keep the car heated, so the trip does not undo the warmth you have maintained at home. Recording his winter routine and warning signs in KinsLe Family Sharing lets a partner or house-sitter follow the same misting, feeding, and watching brief without a handover conversation.