No, cygnets (baby swans of any species) touched by a human will not keep the parents from caring for the cygnets. Many swan keepers and veterinarians must touch and handle cygnets for care and treatment.

The major issue is when the cygnets are taken from the parents for any significant time (more than 2-3 hours in most cases). Once separated for any great length of time, then the parents may abandon the swans. Swan parents are great parents and will defend the cygnets and their territory just like any other wildlife. So, it is important that anyone attempting to get close or touch the cygnets have a very good reason and protect themselves from the defensive parents. The Regal Swan