Nature is unfortunately cruel sometimes and survival of the fittest rules. Swan parents will kill a cygnet if they know something is wrong with the cygnet. There are several reasons for this:

1. The parents do not want a weak or sick cygnet infecting the other brood. So, by killing it, they do not have to worry about feeding or caring for the young bird.

2. By killing the cygnet, they do not have to worry about it being picked up by a predator and followed to the nest or area where the other cygnets would be vulnerable.

3. The swans also do not like the idea of humans picking up their cygnet as they do not know what the ultimate outcome will be for their young and dead is better than abused, etc.

Did you pick-up the cygnet and transport it to a rehabilitator or did you return it to the parents? The Regal Swan