Sexing ducklings - male Khaki Campbell

[GerobakAyam]

According to Metzer, one of these should be male Khaki Campbell and the rest are female Golden 300.
I have a hard time telling the difference.
Can you all help me? Or Metzer got it mistaken?

https://imgur.com/a/xsgzYYN

 

[RisingPhoenixFarms]

I'm not sure exactly but i would say the one closest to the cinder block. All my males tail feathers came in less full, kinda on two sides first, than the females. They later filled out when the drake feather came in.

How old are your babies?

 

[GerobakAyam]

They are 5 1/2 weeks old.

 

[RisingPhoenixFarms]

One should be starting to sound different around now. The girls developing an actual quack and the boy sounding more raspy (kinda like he's got a sore throat). If you can't tell while together i would take one at a time to a separate space to listen.

 

[New duck mommy 2021]

At first glance I would say first one a boy
Only cause it looked like my khaki drake around that age
The head is just slightly darker
I could be wrong though so don’t hold me to it
By 5.5 weeks I usually hear my girls starting to get a little quack in the peeps. The boys tend to keep the baby peep longer