The Rouen duck exhibits pronounced sexual dimorphism, meaning there are distinct physical differences between the male (drake) and the female (hen). Like their wild Mallard ancestors, male Rouen ducks possess a brilliant pattern of feathers that sharply contrasts with the female’s more subdued, camouflaged appearance. This difference is primarily driven by the need for the drake to display fitness during the breeding season.
The Initial Timeline for Drake Feathering
The transformation of a male Rouen duck from a juvenile to a fully colored drake is a gradual process. The first major molt, where the duckling sheds its down for true feathers, typically starts around 8 to 9 weeks of age. This initial change marks the beginning of the transition into young adult plumage, though it does not immediately reveal the full adult colors.
The most noticeable color changes become apparent between 12 and 16 weeks, as the male replaces its duller juvenile feathers with the distinctive adult pattern. The iridescent blue speculum (a patch of color on the secondary wing feathers) is often one of the first features to become clearly defined. The claret breast feathers and the gray flank plumage gradually fill in over the following weeks.
The full adult coloration, including the glossy green head, is the last element of the male’s plumage to develop. This complete color change is generally achieved when the drake is about four to five months old (16 to 20 weeks). The exact timeline can be influenced by factors such as the duck’s genetics and the quality of its nutrition.
Identifying Juvenile Males Before Coloration
Before the bright adult feathers emerge, owners can rely on non-plumage cues to determine the gender of young Rouen ducks. Vocalization is one of the most reliable methods for sexing ducks once they are a few weeks old. Female Rouen ducks retain the loud, traditional quack characteristic of their species.
In contrast, the developing male’s voice box (syrinx) causes them to produce a quieter, lower-pitched, and raspier sound, sometimes described as a hiss or a weak peep. This difference in vocalization is usually noticeable before any significant color change occurs.
Another physical indicator is the development of the “drake feather,” a distinct, upward-curling feather located in the center of the tail. A small version of this defining feature may start to appear on young drakes as early as 8 to 9 weeks of age. Additionally, bill color offers an early clue: juvenile males often develop a yellow or greenish bill, while hens typically have an orange bill, sometimes with darker markings.
The Annual Cycle: Breeding vs. Eclipse Plumage
Once a male Rouen duck reaches maturity, its striking coloration is not permanent. Mature drakes undergo an annual seasonal molt, involving a temporary shift in their appearance. After the breeding season concludes, typically in late summer or early autumn, the male sheds its brilliant breeding plumage (nuptial plumage).
During this period, the drake adopts duller, hen-like feathers called the eclipse plumage. This change provides necessary camouflage, as the duck loses its ability to fly for a few weeks during this simultaneous molt. The drab coloration helps the male hide from predators while it is vulnerable.
The eclipse phase usually lasts for about six to eight weeks, followed by a second, partial molt. This second molt restores the drake’s vibrant breeding colors, preparing him for the next mating season.