A female Muscovy duck is considerably smaller than a male and has fewer, if any, caruncles on its face or at the base of its bill. Caruncles are the fleshy, red, warty bumps found mostly on males.
The feathers on male Muscovy ducks are generally brighter, with the black feathers showing a purple or green tint. Female feathers are more drab in color. While Muscovy ducks do not quack like other ducks, males hiss when threatened, and females verbalize with a soft cluck or churr (a sharp whirring or trilling sound). Males have thicker legs and larger feet than females.