Determining the largest duck in North America requires considering both native species and established non-native populations. Size is often measured by total body length and maximum recorded weight, which leads to a split answer for the title. This distinction highlights the difference between a bird that naturally evolved here and one introduced by humans that has since thrived.
Identifying the Largest North American Duck Species
The largest duck native to North America is the Common Eider (Somateria mollissima), a massive sea duck of the Arctic and sub-Arctic coasts. Individual Common Eiders can reach a length of up to 71 centimeters (28 inches) and a maximum weight exceeding 3 kilograms (6.6 pounds). The male, or drake, averages around 2.2 kilograms, making it the heaviest regularly occurring indigenous duck.
The title of the largest duck overall often goes to the Muscovy Duck (Cairina moschata), which has established feral populations across parts of the United States. A wild Muscovy Drake can weigh between 4.6 and 6.8 kilograms (10 to 15 pounds) and measure up to 84 centimeters (33 inches) in length. Although native to Mexico and Central and South America, its feral establishment in states like Texas and Florida means it is frequently cited as the largest duck on the continent.
Distinct Physical Characteristics
The Common Eider is characterized by its bulky, heavy-bodied appearance, built for life on the open ocean. Males display striking black and white plumage, featuring a white back and chest, a black belly, and a black cap with a subtle pale green nape.
The head profile is particularly distinctive, featuring a long, sloping bill that extends almost seamlessly up to the forehead, creating a unique wedge-like shape. Females are a mottled, barred brown color, offering excellent camouflage while nesting on rocky shorelines. The Common Eider is famous for its insulating breast feathers, known commercially as eiderdown, which the female plucks to line her nest.
The Muscovy Duck, by comparison, is recognizable by its dark, iridescent plumage and the prominent red, fleshy growths called caruncles around the base of its bill and eyes. The considerable size difference between the sexes, known as sexual dimorphism, is pronounced in both species. Male Muscovy Ducks are roughly twice the weight of the smaller females, a size disparity that contributes to their impressive maximum weight being recorded.
Geographic Range and Habitat
The Common Eider is a sea duck, primarily inhabiting coastal marine environments across the northern reaches of the continent. Its breeding range extends across the high Arctic of Canada, reaching as far south as Maine on the Atlantic coast and the Alaskan Peninsula in the west. The birds prefer to nest in colonies on small, offshore islands and islets that offer protection from land-based predators.
During the winter months, these populations migrate southward while remaining close to the coast. They are often found in large flocks in coastal waters, bays, and estuaries, particularly around Newfoundland, Cape Cod, and the Aleutian Islands. These ducks are skilled divers, utilizing their powerful wings to propel themselves underwater to forage for mollusks, especially mussels, which form the bulk of their diet.
Context: Other Massive Duck Species
While the Common Eider holds the title of largest native duck by weight, other species are notable for their size. The Canvasback (Aythya valisineria) is recognized as the largest diving duck in North America, known for its sloping forehead and long bill. This species is a formidable bird, though it does not reach the sheer mass of the eiders.
Other large sea ducks include the King Eider (Somateria spectabilis), a close relative of the Common Eider that is similar in weight and size but distinguishable by the male’s ornate, orange forehead shield. The Common Merganser (Mergus merganser) is another significant waterfowl, often counted among the largest ducks found in freshwater habitats. These species demonstrate the robust size achieved by waterfowl that inhabit the continent’s expansive northern waters.