I originally thought that one of my BOs dropped eggs under my broody Australorp. She hatched 4 eggs 10 days ago, and left the nest. I took the rest of the eggs to incubate just in case- I really wanted some BO chicks. In the past week I have had a chick hatch every 2-3 days(3 so far). 1 more egg wiggling, and one peeping. They are all black- so obviously not the Orps. No one else had access to the nest. Does this happen alot? I'm glad I was able to keep the eggs going- but this is nuts! I will definately mark the eggs next time!