Any ID suggestions on these 2 ducklings?

[Acceber123321]

So I was given these 2 ducklings to care for a month or so ago (now released to someone who has pet ducks and they're doing fine). But we'd like to know what ducks they are.

UK, came off a small river (which is along the back of houses where the cat who caught them lives). We originally assumed they were mallards but they were no where near patchy enough with yellow.


The photo of a single duckling was taken the night they came home.
The 2 of them sat together was after 1 week.
The outside photos (in the black cage) were 3-4 weeks - it was around 4 weeks that one started to "quack" cheepAAAK type noise. We also noticed that one had become more speckled/flecked in the chest around this time too.
The screenshot of them in the paddling pool is around 5 weeks (1 week after release)

 

[Canadian Wind]

They look like they could be black Swedish

 

[Miss Lydia]

Aren't they precious, I agree with @Canadian Wind

 

[Acceber123321]

Thanks Is there any way to tell their sex from the photos? Only one started to attempt to add a vague quack on the end of the cheeps before we released them so couldn't really go from that alone.
And are Black Swedish usually more a pet duck and it's likely these 2 are from a released/escaped pet (or a cross mating?) for the UK? I'll admit I don't know anything about ducks other than basically recognising mallards!

I've just been sent another photo:
Latest duck photo

I can't quite believe how much they've grown! But I'm really glad they've gone to somone who already has ducks.

 

[Miss Lydia]

They are domestic ducks not wild. Now many people dump ducklings once the cuteness wears off so they could be from some domestics that were someones pets at one time.
I just reread and see that you gave them to someone who has pet ducks that's good.
quacks and drake feather are 2 ways, females quack, drakes make a raspy sound like they have a head cold.