You can open the nesting boxes once they are in the habit of sleeping on the roosts. I usually suggest opening them by week 16, since it is possible (unlikely but possible) for them to start laying that age. I actually had a pullet that did last year.
You want them open before they start to lay. They are creatures of habit and, if they start laying elsewhere, they will want to continue laying elsewhere. It is not that unusual for them to drop an egg from the roost or somewhere else when they first start to lay, since it sometimes takes them a bit to gain control of the process, but once they gain control, they will look for a safe place to lay. I am a strong believer in the benefit of fake eggs, by the way.
Another reason to open them just a bit before they start to lay is, if they do start to sleep in the nest box instead of on the roost, you have some time to correct the problem before you start to get poopy eggs. I have had young chickens move from the roosts to the nest box when an older hen started picking on them while on the roosts.
You want them open before they start to lay. They are creatures of habit and, if they start laying elsewhere, they will want to continue laying elsewhere. It is not that unusual for them to drop an egg from the roost or somewhere else when they first start to lay, since it sometimes takes them a bit to gain control of the process, but once they gain control, they will look for a safe place to lay. I am a strong believer in the benefit of fake eggs, by the way.
Another reason to open them just a bit before they start to lay is, if they do start to sleep in the nest box instead of on the roost, you have some time to correct the problem before you start to get poopy eggs. I have had young chickens move from the roosts to the nest box when an older hen started picking on them while on the roosts.
