My 6 week old duck is constantly sitting. It will be following the chickens and my other duck and just plop right down as everyone else continues on. It sits down to eat. It sits down to drink. Is this normal or is something wrong? It is supposed to be a Blue Runner, but I am pretty sure that it is actually a Khaki Campbell. I don't know if some breeds sit more than others. The other duck is a Fawn Runner and is up much more. Please Help.