I would say that your older duck is at least 18 months old (maybe 2 years old or perhaps older) as it looks to me like she has gone through at least one adult moult. Ducks based on black will gradually turn white in the black parts as they get older - usually starting down the back of the neck but also eventually extending over the whole body. The white round her eyes is typical of this too.
I hope I assumed right that you were talking about her colour
Yes that's what I meant. Thank you for the reply. I literally had no idea. Didn't even consider that. I just thought it was plumage. Shd has green in her wings as well ,symèetrical, what coud that be?
Ive just noticed she has a green sheen to her head too... Is that good or bad? Sorry for dippy moment: What do you mean by desirable? Like context wise?
Sorry for not explaining When I say desirable I mean that that's how black feathers are meant to be according to poultry breed standards - black with a green sheen. Ideally, all black feathers should have a green sheen (but not purple). That's what breeders of black birds aim for. So it's good that your duck has a green sheen on her head too
Well, I think her type (shape) is quite good (but I don't know much about Calls). It's a bit hard to tell what her markings would have been like originally. I actually think that she is closer to a Bibbed duck than a Magpie - she kinda looks like a Bibbed that has gone whiter and whiter in the bib, extending onto the shoulders over time. But as I said its hard for me to say. She could breed some nice babies for you
With black ducks that are going white with age - in a show they will usually be beaten by any younger duck that has not started to go white. So mostly people don't show older black females. Interestingly, black males don't tend to go white with age, anywhere near as much as the females.
Blue ducks are the same - they go white with age too. Also chocolate and lavender.
Another thing to check your duck for as far as quality goes is any brown in the feathers - no brown = better quality. Also check for any patterning on her wing bars (that are normally blue green on a mallard). You don't want any patterning of any kind on any black feathers. Also check under her wings. Under her wings should be solid silvery grey (except for the pure white feathers) with no pattern or stripes.
So, green sheen and no brown anywhere are good things and indicate a better quality duck