I had a duckling hatching, it piped externally on day 28 - Thursday morning. By the next day the hole was bigger and we could see the beak. It could breath freely. In the afternoon we left for about 4 hours and when we came back it was dead. There was another hole on the other side of the egg, but it was still within the air sac area (I think). There was a crack going from one hole to the other. But the duckling head was facing the opposite direction - the bottom of the egg ... we think it suffocated. Why did it turned and put its face down there? The duckling looked perfect - no deformities, yolk sac absorbed. Although there was some greenish substance at the bottom of the egg. What happened?