You are very welcome.

We just call these sounds vocalizations because they are a combination of many sounds such as bleeps, snorts, etc. Then, of course the hissing is a sound all by itself to express displeasure or warning.

No, the swans will not crack the eggs and eat them. It is for this reason that we believe that a small animal may have taken the eggs. Even if she went back to protect the eggs, the predator would still have returned to finish the job until all eggs were taken. For the swans to have removed the eggs, they would have had to roll them out of the nest. If the eggs did not make it into the water, then they would be easy pickings for a predator to grab the eggs in the unprotected area.

If the swans are still tugging at, rebuilding the nest and staying nearby, there is a possibility that the pen will lay another clutch of eggs. The Regal Swan