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Common Merganser

Scientific name: Mergus merganser

Common mergansers are streamlined ducks that float gracefully down small rivers or shallow shorelines. The males are striking with clean white bodies, dark green heads, and a slender, serrated red bill. The elegant gray-bodied females have rich, cinnamon heads with a short crest. In summer, look for them leading ducklings from eddy to eddy along streams or standing on a flat rock in the middle of the current. These large ducks nest in hollow trees; in winter they form flocks on larger bodies of water.

Look for them sitting on rocks in midstream, disappearing around the next bend, or flying along the river, when their white wing patches and heavy bodies make them easy to identify. In winter, seek common mergansers on large rivers and lakes; look for them in large flocks mixed with other ducks such as common goldeneye and bufflehead.

Photo: Jay McGowan


31.8-76.2 ounces


21.3-27.9 inches

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Common mergansers dive underwater to catch fish. They also eat aquatic invertebrates (including insects, mollusks, crustaceans, and worms), frogs, small mammals, birds, and plants. They forage in clear aquatic habitats such as streams, rivers, lakes, coastal bays, and estuaries. While they mainly hunt in waters less than about 13 feet deep, in the winter they sometimes venture into deeper waters where fish are schooling. They find their prey by sight, often probing sediments and underwater stones with their slender bills, which have sharp serrations for grasping slippery prey.


These ducks live mainly on freshwater rivers and lakes.  They are rare in the ocean, but they sometimes use saltwater estuaries in winter. Common mergansers usually nest in natural tree cavities or holes carved out by large woodpeckers. Sometimes mergansers take up residence in nest boxes, provided the entrance hole is large enough. On occasion they use rock crevices, holes in the ground, hollow logs, old buildings, and chimneys.

Did You Know?

Common Mergansers are known to form crèches (a bird colony, where one bird takes care of another’s offspring), with single females having being observed with over 70 ducklings at one time.

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