I have a male Mallard duck that I got at the age of about ten to twelve weeks. He was starting to get a little tint of green on his head, a white neck ring, brown chest, and a few gray feathers on the sides. Since we got him, he hasn't really gotten any more male coloring. It is like he is only half molted. He is now almost five months old, and he hasn't gotten anymore coloring. It seems like he is just frozen where he is. Does anyone know what could be going on? I have had other Mallards that were all feathered my 16 weeks.