I have two pullets in a new chicken tractor; they have been in the same place for 8 days. Mostly they are pooping the straw in the covered area and eating/scratching in the run, so the ground isn't too funky. There is still grass, and they are still scratching around (I don't care if they scratch down to the dirt where they are). How often should I move the tractor? It isn't stinky, and there are no flies, and the girls seem content, so what are "rules" for how long they should be in one place? I don't know where I should put this question, so if it needs to be moved feel free!!