How to Identify a Common Merganser (Mergus merganser)

• Head pattern: Male: iridescent deep green head and upper neck, may appear black; rear crown may look elongated but lacks an obvious crest
• Body pattern: Male: creamy white lower neck, breast, sides, and belly with a gray-to-black back and tail
• Head pattern: Female: rusty or reddish-brown head with a shaggy crest, long narrow scarlet-orange bill, and a sharply defined white patch on the lower chin
• Bill: Male and Female: red bill, thick at the base and elongated/narrow toward the tip
• Eye color: Male: brown iris, unlike the red iris of male Red-breasted Merganser

Male Common Merganser lacks a crest and has a white breast/sides and brown iris, while male Red-breasted Merganser has a notable shaggy double crest, reddish-brown breast and gray sides, and a red iris; female Common Merganser shows a sharply defined clean white chin patch versus a less defined, more variable white area in female Red-breasted Merganser The Red-breasted Merganser page lists its own marks.

Wooded lakes and rivers, primarily freshwater; winters on lakes and large rivers, occasionally coastal bays; far more associated with freshwater near the ice line than Red-breasted Merganser Breeds across Alaska, Canada, and the northern US in forested watersheds; winters across much of the continent on open freshwater

Far more frequently found on freshwater near the ice line in winter/migration than the more saltwater-associated Red-breasted Merganser

Shoot from water level if you can, with the sun behind you, so head pattern and the wing patch show their true colors. Get one frame with the bird side-on and one as it stretches or flaps, which exposes the speculum and belly. Note who it is swimming with; ducks flock by species. The app names the likely species; confirm with the marks above, and check the female separately, since females of many ducks look alike.