The Common Merganser is a big, low-slung fish-eating duck that rides the water like a slim white torpedo. The drake is striking in a understated way — a gleaming white body, a dark glossy-green head, and a slender, hooked red bill — while the female is gray-bodied with a sharply defined rusty-cinnamon head and a white chin. Both wear the long, serrated "sawbill" of the merganser tribe, ideal for gripping the fish that make up almost their entire diet.
These mergansers are strong divers, chasing fish underwater on lakes and large rivers, and in winter they gather wherever open water persists — below dams, on the Great Lakes, and along ice-free stretches of big rivers. They breed on clear northern lakes and streams, nesting in tree cavities and on the ground, and the striped ducklings are famous for riding on their mother's back. In Michigan they are most conspicuous from fall through early spring.
Almost entirely piscivorous, diving to pursue and seize fish with its long serrated bill; it also takes some crayfish and aquatic insects. Family groups and winter flocks sometimes hunt cooperatively, herding fish into the shallows where they are easier to catch.
The Common Merganser drake has a clean white body, a dark green head, and a red bill with no crest, and the female shows a crisp line between her rusty head and white chin. Red-breasted Mergansers are shaggier-crested and duller, and favor the open Great Lakes.
To open water — below dams, on the Great Lakes, and along ice-free stretches of large rivers. They concentrate wherever fish are accessible and the water stays unfrozen.
Yes, young Common Mergansers frequently climb onto the female's back to rest and stay warm, a behavior that also protects them from underwater predators and cold water.
Males enter eclipse plumage in midsummer, losing the crisp white body and green head for a female-like brown-headed look. The red bill and larger size still separate them, and the bright plumage returns by late fall.
A raft on the water, though mergansers are best known for hunting cooperatively — a line of birds will drive fish into the shallows together, a habit that makes their groups look organized.
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