How can i tell the gender of my muscovy ducklings?

[Pluto8]

I have a flock of 8 muscovy ducklings ranging from 4-6 weeks of age. I was wondering how could I check the gender of these babies. Is there any methods?

 

[KathiQuacks]

From what little I know, males will be noticeably larger and have longer, broader tail feathers. Not sure if that’s evident yet, you may have to wait a few more weeks.
@Miss Lydia @ruthhope

 

[ruthhope]

I have been wrong too often with Muscovy at that age!!! Muscovy females stop growing around 6-8 weeks when they are about the same size as regular pekins. Muscovy males carry on growing and are noticeable bigger than female clutch-mates by 8 weeks. By 12 weeks everyone knows what they are as drakes can be pushing 12 lbs and may continue to grown until 14015lbs!!! The most reliable sex discriminator is the sound they make. Females have sweet little bubbly sort of voices [except when they go brood!] Males don't have a voice: they huff with their mouths open. Some folks say its a hissing sound, but there is no SSSSS in the sound.