it could be that your hen is getting old and or is sick keep an eye on it and if she or he gets worse take to the vet.
Another Possibility
Hens like to lay in certain nests. If you have a small flock chances are they all lay eggs in the same nest. With the now broody hen occupying the nest and possibly being aggressive toward the other hens, they will need a new "favourite" nest to go to.
When hens are broody they are not 'themselves'. Try taking her off the nest and putting her in a cage, somewhere she is isolated from the other hens and also where there is no nesting box. That always works well for my hens.
Well yes. Sometimes the roosters sit on the nest to encourage the hen to go broody. But roosters don't lay!
If you are asking how to make the hens go broody, then there is no surefire way. To encourage broody-ness, you should put fake eggs in her favourite laying box.
Most hens have a preference as to where they lay their eggs. If a broody hen takes over the communal nest then the other hens will find a new spot to lay. It is always a good idea in a small flock to provide alternate nesting boxes just for this reason. When one hen goes broody, the other hens do not go off laying. If you are missing eggs, it is quite likely that the brood hen is taking what she can find to her own clutch.
Some hens just aren't built for being broody. Although, if there is continuous disturbance, (ie. noise from the house, other hens trying to lay etc), then this would cause her to leave her clutch.
Broody hens do lay eggs. They actually lay one [1] egg every day or two.
It really depends on how good a broody the hen is, and the reliability of your incubator and your experience incubating chicks.
They either have a parasite or they have been fighting.
I have Silkie Chickens who are very broody, they are little bantam chickens that look like little cotton balls.
A broody hen is easy to spot. The hen will remain on the nest when the other hens are going about their daily routine. The hen will often be aggressive when you reach in to remove her eggs. If you remove the hen from her clutch of eggs she will often run right back to the nest, protesting loudly. The broody hen will not roost with the other birds but remain on the nest over night.
They are somewhat protective if they are just laying the egg, and will cackle to draw attention to themselves and away from the nest when they leave it, but after that, they are usually non-committal. However, if the hen is broody and is sitting in the nest to hatch the eggs she is much more protective.
No. A broody hen is a broody hen and will sit on golf balls once the urge to nest takes her. Hens do not instinctively know if the eggs they are brooding are fertile or not. Hens in a chicken coop without a rooster among the flock will still go broody.