I have six hens that are about 10 months old and they have been perfect in every way...that is up until now. They have three nest boxes in a row and on the other end of their coop are three roost bars each about four feet long and each at a different level. Up until now all of the girls went into the coop at dark and all of them got on the roosts and stayed there for the entire night. This was great because it made cleaning up the night poop very easy at it was all in one place. Now one of the girls has decided that she wants to sleep in one of the nest boxes, which I do not like because I don't like the poop in the boxes. For the last several nights I have gone out after dark and pushed the offending pullet out of the box and waited until she hopped up onto the roost. That has been successful because once she has gotten on the roost she has stayed there, but she continues to start the night in the nest box. Why has she suddenly started this and is there anything else I can do to fix it.?