I found a pacific black duckling a few days ago, he was happy enough then, running around and cheeping. he didnt seem too interested in food but he was healthy enough. since then we've kept him warm and taken him for swims and feeding of oats and little snails in the sink. He was fine until today, he seems unhappy and just wants to sleep all the time and when you pick him up he goes limp and just swaks. I'm worried if hes sick or is he just tired?