Subspecies: jamaicensis
1cy male in non-breeding plumage. The dark well-defined cap and the pure white cheek indicate a male, and the diffuse streak through the cheek indicate that the bird is young. The stiff-tailed ducks, like the Ruddy Duck, follow another molt pattern than most of the other duck species. The summer/alternate plumage is the colorful one and all birds are drab in winter, which is opposite to other ducks.
Subspecies: jamaicensis
Female. Likely adult based on the grayish look. In relation to sex, the perception of a brighter and less well-defined cap and dirty cheek with stronger stripe through it are in favor of a female.
Subspecies: jamaicensis
Adult female. Based on grayish tones, and more specific on the fact that older females apparently have longer and more pointed inner secondaries, something I like to perceive in the this photo.
Subspecies: jamaicensis
Second calendar year. ♂. 2cy male. A bird that shows such a white cheek without indications of the dark cheek stripe, and without showing any other traces of the male breeding plumage, I can only conclude to be a young male.