Chickens need to be exposed to heat and cold in order to adapt to those temperatures. If they are kept in mild temperatures then they need to STAY in mild temperatures because their bodies won't have developed the necessary coping mechanisms.
Even the place that sells chicken diapers says it's bad for chickens to keep them indoors for long periods of time. " Firstly, it will make them unhappy. They prefer to be outside. Keeping a chicken inside your home permanently prevents them from expressing their natural behaviors. It is very...