Agreed with above. You should not be allowing them to access boxes (wooden or other), huts, tents, tubes, drawers, piles of bedding, piles of paper, low shelves, under furniture etc. They do not need a special place to sleep and you are basically encouraging them to mate and lay eggs by doing this. It can also impact behavior and cause increased screaming, self mutilation, anxiety and health problems (egg binding, prolapse, etc etc). They all like boxes because they are like nests, but nests are for raising or making babies.
Even if birds are sexually mature, they are less likely to mate and actually produce eggs in the absence of a nest box or shadowy spaces. Trust me when I say that you do not want your birds reproducing unless you have extensive experience in breeding, hand feeding etc. There is also equipment (expensive) that you will need, and since babies will procreate with siblings, the offspring would all need their own cages once weaned (as inbreeding is very dangerous, and this can be a vicious cycle). Additionally, by providing access to such places, you alter their hormone production and make it more likely that you will see erratic behavior (cage territorial behavior, biting, screaming, plucking, aggression, jealousy etc).
