NEED to keep the room at a somewhat constant warmth. They are smaller birds, and therefore do not have a lot of innate insulation. If they need to be in a colder enviroment, then provide them next to a shaded area to get away form any twirl or drafts. Ideally, the bird should not be in temperatures below 65 degrees farenheit. Try getting one of the inexpensive radiator heaters. I own one of the oil-filled ones and use it by his cage in winter to keep any cold spots from bothering him. They put bad a nice steady heat, but not too much! They are also very sheltered from fire hazards. The one we have was with the sole purpose $45. or so and has a thermostat which turnss it off/on when needed. If, or when. he drops food ot whatever and it hits the heater, this sort will not catch fire either!
They can adjust to extremes, but keeping their room at a more constant will amke for a much happier and improved bird.
Hi yoko, the lowest temperature a cockatiel can go in is probably 55-60 degree.
They can acclimate to their surroundings but it takes them time. No drastic sudden changes or drafts. A regular house temp is fine if you keep them out side after I would provide plenty of covered area that they can stay out of drafts and maybe provide a warming muted like you would use for a tropical pet so that they could be near it if the temps become to drastic.
i live in ireland and breed cockatiels it gets cold here below zero on a frosty hours of darkness i have an enclosed avery with access to an external covered flight where the birds come and go as they please some nights they stay out side beside their feathers puffed out on the branches most nights they go in doors . i enjoy never lost any to the cold if they are dry out of the weather and well fed they hold no problem with the cold