dark mallard - juvenile?

dark mallard - juvenile?

Observation - dark mallard - juvenile?. Description: Sorry about the photo, taken at dusk. I saw this very dark (probably black) duck amongst a large group of Mallards and it does not match adult M or F. This was the only dark one. I am not sure what colour juveniles are, or it may be a cross. I do not

Sorry about the photo, taken at dusk.
I saw this very dark (probably black) duck amongst a large group of Mallards and it does not match adult M or F. This was the only dark one. I am not sure what colour juveniles are, or it may be a cross.
I do not think it is a scoter as the bill is wrong, or I may be.