Ducklings don't need their mom, because they are self-sufficient from day one. They only use mom for protection. The problem is that mom will not take it back once older, this means you have to wait until he is 3-4 month old before reintroducing. That way you know he can fend for himself and you don't have to worry about injuries if she may get crazy. This of course will go easier if they can see each other through a fence so they know each other. Some pecking will follow, but that is usually nothing big. Imprinting a duck on a human being can actually a good thing. It helps in controlling other ducks and training them. Boy he or she is so cute. You will have tons of fun. I'm glad that the hatching worked out well. I bet he was quite happy to be free of the darn egg.