Male with unmistakable plumage. The wing speculum design distinguishes female, non-breeding male, and juveniles from other ducks.
During breeding season, the male is unmistakable. It has a green head, purple-brown chest, and gray body. The adult male in eclipse plumage and the first-year male resemble the female, but both are recognizable by the uniform green or yellow beak and tertiary coverts without white tips. In the case of the adult female and first-year female, there are dark spots on the beak and tertiary coverts with white tips.
It is possible to recognize 3 different ages:
Juvenile specimen: gray-brown edge on the outermost tail feather (until moulting in late August), triangular tip of tertiary coverts, greater 4th, 5th, and 6th covert tips with a rounded black mark, the outermost greater coverts with a small white mark.
2nd year specimen: flight feathers and greater coverts and median coverts retained from juvenile plumage, females often retain one or more tertiary coverts. Both sexes can retain tertiary coverts, in this case, they will be worn showing contrast with the rest of the moulted plumage.
Adult specimen: white edge on the outermost tail feather, rounded tip of tertiary coverts, angular black mark on the tips of greater coverts 4th, 5th, and 6th, the outermost greater coverts with a large white mark.
The Mallard undergoes a complete post-breeding moult, acquiring the eclipse plumage, which usually ends in late August in males and late September in females. The post-juvenile moult is partial, changing only body feathers, scapulars, flanks, and tail, in this case, it ends between August and October. Both age classes have a partial pre-breeding moult, acquiring the breeding plumage and changing tertiaries and tail.
Primaries: 10 per wing.
Secundaries: 15-16 per wing.