A chicken is a flock animal. They are happiest with a group of chickens and don't do as well alone.
Our laying hens are in mobile pens that hold about 50 hens. There are no roosters. the dimensions of the pens allow a couple of square feet per bird. Most of the year we move the pens daily. When there is snow on the ground the pens stay put until the snow melts, as it is difficult to get them moving.
The hens tend to stay on their roosts when it is bitter cold. Every year we have a couple weeks of truly life challenging temperatures and we are in the midst of that time. Right now it is 4 degrees. Water is ice.
The girls arrange themselves on the roost so that they can snug into each other. They are going the opposite direction: head to tail each one. Feathers are all fluffed out on mornings like this, as they use every layer of feather for capturing heat.
The roosts are made of wood and not metal so the birds can get a nice tight grip without fear of sticking to metal.
And they stay out of the snow and the wind. The roosts are protected. When the temperature warms up they hop right back down and get to scratching in the earth.
It is the flock and the snugging in that keeps the hens warm. They do it as day old chicks and they do it in the coldest part of winter.