I work at a pond in NY where lots of ducks live, and they like to come up and visit and maybe get a handful of cracked corn, but two days ago one of the ducklings that comes with it's mother and siblings has started limping and walking on what I think is called it's "hock"? It can still swim but it has a very hard time walking, and I don't know if i should intervene and take it to a wildlife rehabilitation facility. What should I do? Help!