One of our hens went broody a few weeks ago. As we have a cockerel, we put 5 eggs underneath her. After 21 days 2 of them hatched, she left the other 3 eggs while she tened to her little brood & they were scattered about & quite cold. Anyway, I bought them in, wrapped them up & stuck them on a hot water bottle. Didn't expect anything from them, but same evening my other half was working in kitchen. This was 3 days after others had hatched. He could hear the baby chick chirping inside the egg! The shell was extremely hard, so we decided to help nature out a little. He carefully made a tiny hole & low & behold, the little chicks beak appeared in the hole. Put it back with it's Mum & now it is 3 days old & looks extremely healthy & happy! Don't know whether it would have made it's way out, but I like to think that we helped. The other 2 eggs were not fertile, but Mum is very happy with her 3 babies!