I've noticed that my chickens actually prefer a darker place to lay their eggs. I think it makes them feel safer. I built a shed-size coop and installed an actual window (about 18"x24") thinking they would want some light. They were laying pretty well but mostly in one box (out of 8!) so I added some curtains at the front of all the boxes for added privacy and now they use them all freely. Chickens are so particular! Hee-hee