What happens if I remove chicks from mother at almost 4 weeks?

[MysteryChicken]

In the wild, a hen will raise her chicks up to the age of 12 weeks before kicking them out of her care, to fend for themselves.

 

[cmom]

My broody's took care of their chicks until they were around 4 to 6 weeks and decided they wanted to rejoin the other birds. It's always wise to have a plan B.