The Common Merganser is a long, low-riding duck built for chasing fish. It dives from the surface and swims underwater with strong kicks of both feet together, hunting mostly by sight, and its narrow red bill has saw-toothed edges that grip slippery prey. Fish make up most of what adults eat, along with mussels, crustaceans and other water animals. In Oregon it breeds commonly in mountain country, and it can be found from the coast to the high Cascades wherever clear water holds fish.
Females nest close to water, most often in a big tree cavity, though rock crevices, spaces under tree roots and nest boxes also work. A day or two after hatching, the ducklings climb to the entrance, jump to the ground and follow their mother to the water. They feed themselves from the start, eating mostly aquatic insects at first, and broods often merge into larger groups after about a week.
On rivers and lakes around Mt. Hood, look for mergansers resting on rocks or along the shore, or watch a female lead a line of young along the bank. In winter many gather on larger lakes and rivers where the water stays open.
How to identify it
A large, slender duck about 22 to 27 inches long with a thin, red, serrated bill. The breeding male is mostly white, with a black back and a dark green head that lacks a crest. The female and young are gray with a rusty brown, shaggy-crested head, a white chin, and a sharp line where the head color meets the pale neck and breast.
Look-alikes
Male Mallards also have green heads but a very different body pattern and bill. Female Red-breasted Mergansers are similar to female Common Mergansers; a crisp white chin and a sharp border between the rusty head and pale breast point to Common Merganser.
Habitat
Clear lakes and rivers surrounded by forest, with large trees near the water for nest cavities. In winter it moves to larger lakes, rivers and sometimes coastal bays where the water stays open.
Sightings in the forest
138 research-grade sightings in Mt. Hood National Forest on iNaturalist, most recently on October 31, 2026. See them on iNaturalist →