So my chicken is tucking his head into his feathers...

[229Mick]

First time I saw this, I had no idea what was going on, but it appears that one of my chickens has the habit while roosting, of turning her head almost 180° and then tucking it into the feathers on her shoulder. Anybody ever seen this?
The photo is through the window and the screen, so it's not the clearest, but you can see the two of them for comparison...

 

[ll]

I wish mine would do that to keep their combs warm in winter!