How do broody hens stay healthy for 21 days??

[Johnchickens2]

Ive always been interested to know. While brooding, they go out only once or twice a day - it doesnt seem to be enough in order to stay healthy. And it lasts 21 days or a bit more sometimes!
How do they actually stay alive?

I have also noticed that when my broody hen takes her daily break, she isn't that interested in eating. She eats here and there but she is MUCH more interested in taking a bath. Most of her break is spent for bathing, and only a few minutes for eating and drinking. Is it normal?

 

[Johnchickens2]

She doesn't fill her crop with food and water, like I would expect someone who eats only once a day, to do.
I myself would eat as much as I can before returning to the nest

 

[NatJ]

Any chicken can eat a lot of food very quickly, when they want to, so your broody may be eating more total food than you realize. But yes, consumption does go way down.

A broody hen does not need to eat as much as a laying hen, for several reasons:
--she is not laying eggs
--she is less active
--where a laying hen has a bunch of egg yolks getting big and ready to lay, a broody hen absorbs those again. This causes her to "lose weight" while broody, as the yolks get absorbed and the reproductive organs shrink. "Losing" this weight does not harm her.
--a broody hen uses her stored body fat while broody. This also causes her to lose weight while broody. Considering how much fat some hens store up before going broody, losing part of it is probably very good for her!

It is possible for a broody hen to die of starvation, if she uses up all the egg yolks and the stored fat and does not eat enough other food. But it is fairly rare. Most hens will either start eating more food, or stop being broody, before that would happen to them.

 

[sdm111]

Sometimes I have broodies hatching 2 or 4 clutches straight and they've always been healthy. As long as they are in general good health they are fine. I have 2 now about to be 3 in a few days

 

[rosemarythyme]

I believe they store up fat in their bodies in anticipation of brooding and partially survive off of that.

 

[TheFatBlueCat]

They DON'T stay healthy, which is why it's important to stop them from being broody if you don't have fertile eggs for them to hatch. They come up off the nest much lighter and a little ragged, and by the time they decide the kids are alright on their own, they look very worn out!
The high protein chick-starter feed helps them get a head start on gaining back their weight and feathers. In my experience brooding is so rough on them that if you have a broody she will not need to moult, the broody moult is enough. I have two hens that raise at least 2 rounds of chicks each every year and they never had their 18 month moult, or any moult aside from the feathers they lose while raising the chicks. I've had them since they were 5 months old.

 

[Perris]

Ive always been interested to know. While brooding, they go out only once or twice a day - it doesnt seem to be enough in order to stay healthy. And it lasts 21 days or a bit more sometimes!
How do they actually stay alive?

I have also noticed that when my broody hen takes her daily break, she isn't that interested in eating. She eats here and there but she is MUCH more interested in taking a bath. Most of her break is spent for bathing, and only a few minutes for eating and drinking. Is it normal?

They have evolved over million of years to do this; the ones that do it well get to reproduce and the ones that do it badly don't pass on their genes. And as rosemarythyme indicated, they get themselves into tiptop condition before they start. And as FatBlueCat said, it takes it out of them.
I have one who is more interested in dustbathing than eating too. It's vigorous all body exercise for her, as well as a way to scratch an itch. She's not burning through as much energy as normal either when sitting still for 23 out of 24 hours.