It's to make extra room in the coop, it makes it less likely they'll use the box as a perch and it makes it so you can collect eggs without going through the pen or in the coop (can't walk into out coops anyway, they are all elevated).
I love it, great idea and job. It should really make your coop cooler (and cool to look at, LOL)
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I keep everything outside of the coop. I don't want them spilling food indoors and you don't want to add a source of moisture (mold, ammonia, etc) inside the coop. As dry as possible is your friend. I currently use the commercial type hanging feeders that hold 40# of food in each run. I had to add the lid to each feeder to keep out roosting birds and blowing rain. But I'm still not happy with them and am working on converting to homemade PVC feeders for each pen that can be filled from outside. We use the commercial double wall waterers and pans in all our runs for water (the first two coops have automatic water founts). This is a HUGE source of work for us and they are all being converted to an automatic water nipple system. In fact, there is a bag of 50 chicken nipples sitting next to my computer with paper and pen. I'm currently designing the layout for the first bank of cages and we're going to Home Depot for PVC and fittings tomorrow. I can't wait to get them converted, less work and cleaner for the birds.
My next project is to add misters around the top of all the runs before the heat gets too bad this year and add more permanent roofs over all the runs before next winter. Only three runs had permanent roofs and I loved them. We added tarps over some of the runs, but when the rain was bad I would still get muddy messes. My mother's day gift is supposed to be my son coming over and shoveling three truckloads of sand for me. Start/end of winter all the runs get a fresh layer of sand. Right now my pens look like packed down concrete (mixture of sand, dirt, spilled feed & droppings cemented together).
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