Ashland Park swans killing, eating ducklings
Crazy swan kills and eats duckling (almost)
These swans just attacked or killed goslings or ducklings without apparently trying to eat them:
Swan drowns duckling (in this case a Coscoroba Swan)
Killer swan (attacks gosling without killing it)
Smaller waterfowl sometimes eat ducklings:
Duck eats duckling
Ok, swans probably mostly kill ducklings and goslings (and sometimes even adult ducks) out of territoriality rather than to eat them, but this isn’t unusual behavior. And while ducklings are a bit larger than their usual fare, swans are quite capable of eating one (and sometimes do).