I have five, three black and white and two that are mixed colors. They are the friendliest ducks I've ever seen, but have no clue what two of them are! Two of the black and white ones are boys. They are giant, 3 times the size of the black and white female (pretty sure its a female), but only about twice as big as the other two in question. Here is the black and white "female": Here are the two in question: I thought they were boys too, but they are more than 1-2 weeks older than the rest, and they are no where near as big, although they are a little bit bigger than the female. What are they!?!?