Common Merganser is a large, streamlined “sawbilled” duck measuring 22–28 inches in length with a wingspan of about 34 inches. Adult males have gleaming white bodies, glossy iridescent-green heads and red bills, while females and immatures are gray-bodied with a rusty-cinnamon head and subtle crest; both sexes sport prominent white wing patches in flight.
In Arizona, Common Mergansers occur chiefly as winter visitors, forming small flocks on large open waters—reservoirs, rivers and lakes—where northern populations retreat when ice forms farther north; they are recorded statewide. Although primarily a boreal nester, rare breeding has been documented in Arizona: small numbers nest in the White Mountains and just below the Mogollon Rim, with isolated summer records from Bonita Creek and Many Farms Lake in the northeast .
These ducks forage by diving for fish—using their serrated bills to grasp slippery prey—and also take aquatic invertebrates such as molluscs, crustaceans, worms and insect larvae; in Arizona look for them on larger lakes and along river systems like the Verde, Salt and Colorado during winter.
