The Lake Duck is a stiff-tailed duck of southern South America, primarily in Argentina and Chile.  They are found on many inland bodies of water, favoring freshwater wetlands and small lakes.  Males are handsomely patterned with a chestnut body, black head, and large, blue bill; females are brownish marked with a contrasting pale subocular stripe and throat.  The species is remarkable in that the males have the longest penis relative to body size of any bird; the organ has apparently evolved a brush-like tip to remove sperm from previous matings.