My birdroom/coop was 70% humidity. When I put the hygrometer under a broody it rose to 80%. I expected it to go down. My hygrometer is cheap so the numbers mean little, but it does indicate that broody hens not only provide the right temperature, they also provide the right humidity. My tentative conclusion is that it does not matter what the humidity is in the surrounding air, the hen's body provides the right humidity for hatching.
