Why do you "need" to separate a good Mama hen from her chicks? Why mess with success? You're going to upset the hen, get her permanently angry with you, and she will communicate all the more strongly to her chicks that You are The Enemy.
Why not win her & her chicks over with kindness? Bring little treats every time you go to see her. Chopped hard-boiled egg, little bits of bread, and as they grow, fine cracked corn, apple slices, melon rinds, & more.
Put them a few yards away from you, where Mama will find them & buk-buk-buk call her kids over for the treat. Just sit there and talk nicely to them. Soon they will all begin to associate your approach with good things.
You can train them to come to you by calling "here pik-pik-pik!" and shaking a bit of scratch or feed in a can right before you give them their treat. Like Pavlov's chickens, they'll quickly learn to connect that sound with treats. Occasionally make that call & sound withOUT giving a treat, then you'll have them as hooked as gamblers, not knowing for sure when the payoff will come. This will also help if you need to call your chickens but don't have a treat handy.
Chicks raised by a Mama hen are usually more "wild" -- actually cautious-- than brooder chicks, but I think they also are smarter & have better instincts. They can also be courted with kindness either as little chicks or later when Mama is done raising them. Be patient & don't bother them unnecessarily.
