In August we were given 4 ducks, 3 white with black spots and 1 grey/black/white. They have doubled in size since then. Two of the whites are larger and heavy, one white and the grey/black/white are smaller and can fly very well. They make very little noise and I don't see any curly tail feathers. They also have not laid any eggs. So now I wonder, am I feeding drakes or hens? I assume they are a cross of some sort would that be correct? Any help would be appreciated.