Molting and broody question

[raro]

I've had chickens for about five years, and never have had a chicken do a "full" molt, just a thinning of feathers. And rarely does a chicken go broody for me.
Well, now I have a beautiful, glossy black Sumatra who has been broody for about 3 weeks. Is this normal? I go out there several times a day and she's sitting in the henhouse very quietly on her eggs. Okay, fine. But today I picked her up and she was not happy about it, so I just held her on her back like a baby, and was startled to see that her tummy was entirely bald.
Is it normal for a hen to only molt on her underside like that? She seems fine otherwise.

 

[ChirpyChicks1]

They pull the feathers out on their belly to help heat the eggs

 

[raro]

Really?! I have never heard of that! Thanks, that makes me feel better. I was just letting her be broody, figuring she'd get out of it sooner or later. It's good to know it's normal.

 

[ChirpyChicks1]

Completely normal, good luck! I have yet to deal with it myself but really don't mind considering I don't have a rooster.