Silver Appleyard mix duck gender help?

[chickenmama22]

I have 5 adult ducks -- a silver appleyard drake, 2 silver appleyard females, Bob the black runner drake and a pekin female.

Here are their offspring:

Is it obvious which ones are males/females? I generally raise chickens and don't know much about duck gender. Once the tail curls, I can figure it out. Is there a way to tell by the coloring?

Thanks in advance!

 

[Lanicus]

Since they are mixed breeds I think it would make it harder to tell, although they look old enough to be able to voice sex-meaning the females will have a loud quack while males have a much quieter whistle