The length of the smew is 14 to 17.5 inches, the weight: is 1.1 to 2 pounds, and the wingspan is 21.5 to 27 inches
The drake (male) smew is striking and unmistakable with a mostly white body marked with a black eye patch, breast bar and v-shaped nape patch beneath the crest. The eyes are black and the wings are dark with large white patches.
The hen (female) is smaller than the male and has a chestnut head, white throat, and dark brown eyes. The breast is light grey and the rest of the body is dark grey. Juveniles resemble the hen, but the central wing coverts (coverings) have brown edges. The smew’s black bill has a serrated edge with a hook at the tip. Its legs and webbed feet are grey. As with all ducks, the females molt when the chicks are half grown; the males slightly earlier. The ability to fly is reached by the young and regained by the adults in late summer when the family is then ready to begin the fall migration.