I have 3 hens, and they are getting old enough, so I built them a nice 12"x16" box. Well, they totally stay away from it, no matter where I place it. I dont know how to get them to hang out in it, they seem to prefer the dirt. The run is 6'x12'. They roost at night in the center of the run in a raised plastic dog house, where they never go during the day. The only thing I noticed is they are starting to create nesting areas right in the dirt, they like to "nest" right next to each other; should I have made the box big enough to accomodate all 3?