Chicken tractor

I've promised a few folks that I would upload pics of my chicken tractor design. It is an Aframe design,

the top 1/3 is roofed.  Under the roof is a roost, and the bottom is completely open to allow the droppings to fall on the ground. No cleanup! There are two nests with access doors on either side of the roofed areas. The only bummer is that in the winter the birds get completely drenched. Clear, corrugated roofing placed over the sides would probably work well.