In the history of humanity, there have been a lot of differences in how we looked. The Ducks should have made an evolutionary journey as well. I have made this time line (not very good quality ). I would like to hear your thoughts!
Interesting. I'm not too knowledgeable when it comes to the evolution of birds, but I think the first one (the bird in the nest) should be removed. Anthropomorphic ducks (like Donald) and real birds (like the one in the picture) most likely share a common ancestor, similar to the relationship between humans and chimpanzees. Humans didn't evolve from chimps; they're our "cousins". The same is likely true for Donald and that bird. But then again, I don't know how the evolutionary history of birds work.
It's weird to think that every other anthropomorphic species in the Duck-universe (dog, mouse, pig) would have gone through a similar evolution, parallel to the "cave-ducks". For some reason I think a "cave-pig" would look interesting.
edit: Wait, I just noticed that the little brown bird-baby in image #2 actually appears to be some sort of dinosaur, what with the tail and such. Birds evolved from dinosaurs, I know that much. So yeah, that first bird in the nest in image #1 should be some sort of cousin to the anthropomorphic ducks.