They sure do know what they are doing. Last year I had a bantam hen go broody in July. Just a few days later we got the heat wave and had temps between 102-106 for 2 weeks straight. I know it was hotter than that in the hen house. I just knew there was no way that hen could hatch chicks. I noticed that she did not sit tight on the eggs like they usually do,but lifted herself up,exposing the eggs. She hatched 2 chicks(both pullets) which I think was pretty good,under the circumstances.