I have moved from incubators to letting to broody chickens do the hatching. The success rate has increased to 90% - 100%. I had one chicken sit on three guinea eggs and they all hatched, and another chicken sat on four guinea eggs and they all hatched also. It's funny to watch, the guineas are all about four months old now and free range with their adoptive mothers. The guinea parents stay with them also. It's like mom & dad & kids with a nanny.