I have chicks that look the same age as yours.
Mine will not roost yet and are happier just standing on a skinny block of wood on the floor.
Perhaps lower the roost and see if that works.
maybe something flat. like a 2x4 with the flat side up. by the looks of your tractor you should be able to make a supports for the 2x4 come up off of your bottom floor rails. then all you have to do is mount the 2x4 from one side to the other.
Chicks don't seem comfortable with "roosting" until they're at least a few months old and even then it's sporadic. They seem to feel safer just huddling on the ground. If they were with their mama she would stay on the ground with them for at least the first 2-3 months. Our chicks by mail seemed to just enjoy jumping on and off of perches during the day just for playing around sake.
Amy J.
I just put a roost in for my girls last night.. LOL actually I called it a "training roost" since it is maybe 1.5 in off the floor! I basically nailed a long scrap of 2x4 to two scrap blocks of wood. They don't sleep on it.. well one (my fav. little Sally) tried, but her sisters and brother weren't done pecking at the thing yet, so they scooted her off! Mostly they just like to peck it, and hop on and off. They seem to prefer huddling on the floor to sleep. They can't kink their necks at odd angles on the roost, after all!
My chicks started roosting when they were two weeks old. I just put a couple 2x4's up on their edge in the brooder box and they were happy. They all used the temporary perches.
At 8 weeks, they were flying up to their night-time roost 30" off the coop floor and were happy there as well. In their run, I put their original 2x4's which had been used in the brooder and they loved it.
It is never too early to introduce roosting. The size of the roost depends on the breed of chicken. Bantams don't need something as large and sturdy as standards. Standards like to have something they can "lay" on as opposed to "perch"; therefore, standards prefer a 2x4 layed flat so they can lounge on it.