Cayuga duckling about 4 weeks old doesn't seem to be able to walk around very well. Legs are shaky and it seems to be walking on it's own feet all the time. The other two are doing fine. This one is getting up and drinking and eating, just seems to be shivering. Even under the brooder lamp. This is the first time I've had ducks so I'm not sure what to look for. They have abundant supply of fresh water and food. A little rubbermade pond with the water changed every couple of days. Fresh greens daily. I've even managed to give them some small slugs to eat. I don't want to loose this baby. Just noticed this the last couple of days. They're sort of hard to tell apart. Their brooder is next to my chicks brooder. 100% positive that they haven't gotten hold of any medicated feed.