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.
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.
2417 (2 photos) 2016-10-25 Villa di Borghese, Rome, Italy
Young male. Female-type plumage but beginning greenish bill.
2418 (2 photos) 2016-10-25 Villa di Borghese, Rome, Italy
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.