Ok, this is getting crazy. The same hen, Mohawk, is broody again. This time, we can't blame it on hot weather, or on a change in routine. No, she simply goes broody at the drop of a hat.
Our cure for broodiness is to put the hen in a smaller cage, elevated off the ground. The cage is upside down so she has only the mesh ceiling to walk on. We give her food and water and just leave her in the cage for three days and then she seems cured. She goes several weeks or months before getting broody again.
I wonder if we could get some fertilized eggs and let her hatch them... Our city won't let us keep them, but we could hatch them.