He eats All Flock, and the rest of the ducks eat it too. My runners have extremely bright yellow bills, and everyone is healthy.
I've never seen a mallard without the black spot, that's cool.
@Kroelies , that is almost exactly the color of his bill, except he has a black line in the middle...
I have two mallard drakes. They are not rouens, but true mallards. They were hatched in June, and have been in breeding plumage for months now, but one of them still has a olive green bill. Is he lacking some mineral or something, or is it just a rare genetic thing? He is extremely healthy, and...