I have 2 broodies. The "Broody Coop" I had for the last broody is currently occupied by the month old chicks she hatched. So I built a broody box. It is like a little doghouse with a hinged, shed-type roof. It's "foundation" is made of landscaping timbers. (The lace curtain panel is for shade.) I had both broodies in there, but that didn't work out too well, so I built another one. I estimate that it cost me about $25 to build.
