If the cygnets are able to fly, then it is possible that the other cygnet flew off either looking for another area or got lost. If it got lost, it may or may not find its way back. The other possibilities are that if it did get away from the other swans, it was taken by a predator or the NJ DNR as the NJ wildlife officials intentionally kill the swans. They and other states do not want Mute Swans in the state as they are trying to free up habitats so they can introduce the larger Trumpeter Swans for Trophy Waterfowl hunting purposes.

Hopefully, none of these cases are the problem and the swan will either come back to its mother and sibling or it is doing well in another area by finding another flock of swans, especially juveniles so that it can begin the bonding process for a future mate. Since this is now the migratory season, more than likely it is time for the swan to leave and go find another flock so that pairing can result.

Generally, the cygnets and parents will stay together until 9-10 months of age, but if the cygnets can fly and have learned how to be swans and protect themselves (which usually is the case after 6 months of age), they can fly from the habitat in search of potential juvenile mates and new food, shelter, habitat resources.

If the cygnet is a male and there is no adult male, then when the juvenile comes of age, it can and will mate with the mother with no problem. It could also mate with its sibling. Regardless, unlike mammals, this mating should not produce any genetic anomalies. The Regal Swan