Question on Blue Swedish ducks

I was just wondering if the blue swedish ducks are like the pekin where the males have the curl in their tail and the hens do not I have a few here, and do not want to butcher them all if I have at least 1 hen in the bunch. I would love to keep the hen and a drake, but am unsure about sexing them. Thanks for any help!!

EVERY drake, except Muscovy drakes have a sex curl on their tails. The only time they don't is if they are molting, then they go into an eclipse plumage and loose it for a bit, but will come back once they feather out again.
You would hear it in the quacks too, your females are going to have the loud quacks, the males more of a raspy quack.

I don't really hear any difference in the quacks which is why I was wondering about the tail curl! Thanks