Subspecies: platyrhynchos
Adult male with the yellowish bill. Abnormal form. The classic one with the white breast. Apparently both wild and domesticated birds can show these different plumages. However, it is fact that most of these are seen in parks and similar places away from 'real' wild nature.
Subspecies: platyrhynchos
The underwing looks strange, guess that it is because it is a young bird - a male due to the strong shift between the brown breast and the white belly.
Subspecies: platyrhynchos
Immature. ♂. Young male. Aberrant type. You can see the beginning greenish bill typical for the males. Wild bird in park.
Subspecies: platyrhynchos
Guessing young male still with completely dark bill. Male because it looks like it has a greenish cast to the top of the head (are these aberrants always males?). With normal male. Aberrant type commonly found in human surroundings.
At one point all the male ducks standing along the shore were spreading their tail like this. A courtship detail? though there didn't seem to be any intersexual activities going on.
Adult. ♀. New balcony species! Whether attracted by the other birds constantly visiting our feeder or looking for a potential nesting site, I shall not say. But it took off right away, when sensing that it was being watched by the Big Eye...