Thing is is that I’ve got 2 roosting bars that are lower down that the babies can reach but momma is a top hen so she’s always on the highest bar. The lowest bar is only 1 foot off the ground. I’ve got a couple juveniles & my rooster that don’t use the bars. Instead they either use the ledges infront of the nesting boxes or the floor to sleep. My rooster sleeps on the ground right in front of the coop door. 3 of the 5 babies where actually under him last night staying warm. He’s a good daddy.
If the rooster is willing to let them snuggle beside him, they should stay warm enough, so no need for you to remove them.Then should I bring them in at night to keep them warm & then back out with all the others 1st thing in the mornings?
Conversely I would consider manually moving mama down to a lower bar once it's dark, and then moving the chicks up there with her, so they can warm themselves up next to her. She may or may not stay, but if she does, it'd keep the chicks warm and also start teaching them that roost = bedtime. In a perfect universe she would be encouraging them to roost with her first before completely weaning them off.