Hello - A mallard duck nested in my second story window box. After 5 of the eggs hatched she called for them to jump and leave the nest. However, one egg was left and was just cracking though. My motherly instinct kicked in and I brought the egg in and took the baby out of the shell and kept it warm. It is now 4 days old. I have been feeding it and keeping it warm. This morning, I saw what I think was the mother and I put the baby outside where it began to cry - the mother came to it but the baby did not follow the mother. So the mother left. What do I do?