Thanks for all the replies. The main reason I hope they learn to roost at night is that I don't want to deal with matted poop on their rears. I dealt with that when they were young and really don't want to have to wrangle an adult chicken to cut big poop ball out of their feathers. :-)
So, my four chickens are almost 12 weeks. They have a beautiful coop and run. I've blocked off the nesting boxes for now. But they are not using their roosting ladder. My coop is built from old windows, so they have plenty of light during the day. The only light they have at night is from an old...