I agree this is key. Our winters are mild and the birds thrive during the cooler months. -no heat required, here. (We, unfortunately, have some birds that seem to really struggle during the summer heat. -didn't research breeds enough before purchasing.)I think a key point is right at the start of the article
"Choosing the right type of chicken for your environment is a very important factor not to be overlooked."
I can't fathom temps below 0.......much less -40!!! Oh my!!