When the temperature reaches 12 degrees at night, cockatiels will feel cold, so insulation measures are needed. Cockatiels are tropical birds that are relatively sensitive to temperature. When the temperature is too low, they may catch a cold, which may even be life-threatening. Therefore, it is recommended to raise cockatiels indoors, control the temperature at about 20 degrees, and feed them some food with high fat content. If the cockatiel is still a young bird, you can also add a protective cover to the outside of the cage to keep it warm.

To sum up, cockatiels need to be kept warm at 12 degrees at night to ensure their health and safety. For more information on raising cockatiels, it is recommended to consult a pet doctor or an experienced parrot breeder.