My son raised this duck from a duckling. We got her for him for easter this year. She is a mallard. We have to put them up in a building at night because something got in the pen and killed both our males. We got the girls out the next day and put fresh water in the pen. All of them played in the water. A few minutes later one by one they started acting funny. They were stumbling around and when I picked them up their body temperature was very cool. I set them in direct sunlight and 3 of the 4 got over it. They are acting just fine but the one can't shake getting cold. Her head droops and she stumbles. All this happens when she gets cold. She eats and acts normal when she is warm. Right now I am keeping her in the house in a pet carrier and I really need help. I love my ducks and I don't want to lose any of them. I have heard you can give them apple cidar vinegar as a supplement. I have also heard about giving them poultry vitamins. This is our first flock of ducks and I want to do what is best for them.