The male mallard, or drake, has a green head that is translucent in the sun. They have a white ring around their neck, an greenish-yellowish colored bill, dark reddish chest, and gray body. Females are mottled brown with a black line through the eye, and an orange bill with brown splotches. Both have a blue with white border patch on the tailing edge of wing. When immature, the male and female mallards look similar. Before winter, ducklings shed their feathers and grow new ones that are the feathers of their adult gender. Juveniles have brown outer feathers, while all adults have white ones.
Worn feather are replaced twice a year, in the spring or early summer, after breeding and in the fall. Body feathers are molted twice, while the wing feathers are only shed once a year. The wing colors are always the same.
In the spring or early summer, after the females lay eggs, males will shed their bright green feathers and grow brown ones, similar to the female. The spring molt is a partial loss of feather when breeding season ends, they are flightless for a couple of weeks. While they look like the females, the male bill is still greenish. This is called their eclipse plumage.
The fall molt is the loss and replacement of all feathers in a short period of time. They are usually flightless during this time as well and the basic adult plumage emerges. This occurs before the next breeding season. Females molt have they finish raising their ducklings. Their colors are always the same.
Read more about mallards here: DUCK PONDS IN THE LATE FALL