Hen raised vs brooder question

[SJS66]

For the first couple weeks mine were sleeping on their branches in the brooder, but then they took to sleeping on the floor sprawled out under the lights like puppies sunning themselves. I'm not sure why they stopped perching.

 

[Artistickatt]

Mine went back-and-forth. I have this theory that their wings start getting heavy because they’re feathers start coming in and they’re tired or they are unprepared for darkness and dont know or think to roost. My first ones didn’t have a “roost” available until they were 8 weeks and were at to the sunning sprawled out stage on and off from 4 to 8 weeks. They happily migrated permanently to the branch roost when they got outside. My little ones now, are 6 weeks, and seem to still want the ground for now.