[CONTEST] Identify this bird for 20k! - NOW OVER

Yes and no. Geographic isolation sees similar animals evolve to different traits due to coincidental location. However, these differences are usually enough to cause speciation, or a difference in species entirely. Take for example the Nebraskan bird the western meadowlark. It looks and behaves almost exactly the same as the eastern meadowlark. Their coincidental separation caused them to develop different songs, thus they no longer communicate and breed. That is why there is now two species instead of one by the standard definition of a species, which is the ability to produce fertile offspring between two creatures.

In theory then a population could separate and develop a new song. Though, they may still find a way to communicate. There are universal signals for "danger" and "stay away" amongst animals, typically. The bird type could develop a mutation trait within a portion of its population that helps them communicate with previously separated counterparts (who, by the way, have now somehow found their way back; again coincidentally). If this is the necessity for survival and thiving, then it will continue to be passed down, temporarily creating a selection of "translator" birds until either they or the *unfit* population selection without the trait die out. Or... you get a third species. The middle paragraph here is entirely speculative...

As far as "studying" a language, plenty of birds mimic. They can garner if certain warbles are friendly or not, essentially deciphering their meaning. Such has been seen in what you would call the "intelligent" or even "tool using" birds, such as parrots and crows (e.g. African Grey parrot).

#biobirb

Though this surprised me after researching it a bit, as this bird grows to be a lot larger than the one I saw, it unmistakibly exhibits the same markings (grey head, black tail-feathers, brown body, lighter chest, black eyes and beak, etc.), has the same body shape and mold, and this website has a picture of a South African Shelduck that is written as being taken at the San Diego Zoo's Wild Animal Park, providing support for the location. Thus, this seems to conclusively be the correct species.

Do I have agreement on this?

I agree. Let me know who said this and I'll send payment.
Finally, I think i had nightmares about this.

Found your post:

Just missed it earlier because of the lack of a picture, but either way, unfortunately as dictated by the main post, if the sex of the duck changed how it looked, I'd asked that that be specified:

As the female South African Shelduck DOES look different than the mystery duck (has white facial markings), this applies, so unfortunately I cannot count that post as the official winner. I'll send you a 6.5k bonus tip and a Hashhog head for your efforts, though.

As AverageWalrus was the first to identify both the species of the duck and the sex responsible for its markings, the prize money goes to him (in response to Krysyy). Guess he wasn't as easily stumped in the end as I thought. Congrats to him!

Related note: I think I've looked for ducks and Doctor Who too much recently...
This came up on my FB news feed:

Looked up the female Ruddy Shelduck, and the head seems to be more of a cream color rather than a gray color in the vast majority of individuals for the most part.

As for the Cape Shelduck, the Cape Shelduck is also known as the South African Shelduck, which would explain why they look so similar: they're the same bird.

I'm going to run to Target and get some new batteries for Krysyy... I think she's broken.