I have a 4 yr old male duck. Lately he has developed a slight limp, he's always thirsty and has a huge appetite. Tonight I noticed his vision is not so great. His poop is extremely watery, but I am chalking that up to the large amount of water he drinks. Plus at the end of the day he will fall asleep in my arms. He is mainly a house ducks, but does forage or play in the lake for a few hours a day.