We have seen this activity in several swan pairs, more in black swans vs mute swans, but it can happen in various species. Out of curiosity, what species of swans do you have?

If the female decides to re-sit on the nest to hatch more cygnets, then the 7 week old may be abandoned and neglected. If this is the case, it will eventually die from a predators attack or not being able to procure food from the bottom of the pond since its neck is not long enough to reach aquatic vegetation.

A swan mother can count and knows exactly how many eggs she is to lay at one time (this usually is an attribute that is part of the female swan's genetic make-up) and she also knows how many eggs have hatched. By taking away the cygnets at a young age, the mother is trying to re-hatch and raise this genetic number.

This situation is why we suggest that no cygnet be taken from the parents until approximately 5-6 months of age. This time allows the parents to be parents and allows the cygnets to understand that they are a swan and learn swan behavior which will include how to protect themselves from predators which is something that humans cannot teach. By 5-6 months of age, the parents will also be ready for the swans to leave and will start forcing them from the area. The Regal Swan