Sexing these guys?

[BlessedChaosHomestead]

So these guys are all 5wks old. I have 2 Swedish Blue, Welsh Harlequin and do I have a Mallard & Rouen? Or 2 Rouens??
Can any of these be sexed via coloring; bill coloring, feathering?

This one here is really small; hoping it's a female, but it's actions are those of the crazy one we had last year that turned out to be a drake mallard. *facepalm*

You can see the size discrepancy here. lol That's a small little duck. lol

Baby photos are below:

 

[AnnieDuck]

Both the size of that one with the others and it’s baby picture says mallard. It was the one on the right in their baby picture? I would guess 1 Rouen and 1 Mallard. I can’t guess genders yet on them, and don’t be surprised if you see green on their heads either way- my girl Rouen had green on her head stripe.
The Welsh Harlequins I would guess both male because of their bills’ bean color as babies, their darker heads now, but mostly because of their olive colored bills.
I don’t know anything about Swedish but yours are very pretty!

 

[HennyPenny44]

Based on beak color which is supposedly 90% accurate, you have at least one Welsh Harlequin male, maybe 2. I ordered 4 females from Metzer and they all had pinkish/tan beaks with darker tips whereas the 4 I hatched out a couple of weeks before that were 3:1 or 2:2 grey:tan with dark tips beaks. One was a bit iffy. Here’s the older ones I hatched out now at 1 month. Two of them have a darker chest/grey bill/neck ring and two have a lighter chest/olive bill. Not sure if the chest color or bill color mean anything at 1 month.

 

[BlessedChaosHomestead]

Based on beak color which is supposedly 90% accurate, you have at least one Welsh Harlequin male, maybe 2. I ordered 4 females from Metzer and they all had pinkish/tan beaks with darker tips whereas the 4 I hatched out a couple of weeks before that were 3:1 or 2:2 grey:tan with dark tips beaks. One was a bit iffy. Here’s the older ones I hatched out now at 1 month. Two of them have a darker chest/grey bill/neck ring and two have a lighter chest/olive bill. Not sure if the chest color or bill color mean anything at 1 month.

Well if the dark tip means something, I do have one female then. Unsure on the other still.
Hoping I have more females than males.

 

[HennyPenny44]

Well if the dark tip means something, I do have one female then. Unsure on the other still.
Hoping I have more females than males.

That’s the prevailing theory. Metzer supposedly no longer breeds for beak color as they deem it unreliable and they just use vent sexing. But all the females they sent me had the dark tip on the beak. I have no experience with other breeds of ducks so I’m not sure of the others’ sexes.