♀ Red-breasted Merganser on Lake Ontario @ Ward’s Island, Toronto (March, winter, midday, sunny, -9° C).

The female  red-breasted merganser has a dusky gray back enlivened occasionally by a small white patch in front of the tail. Except for their smaller size, female red-breasted mergansers greatly resemble common mergansers. They have cinnamon-brown heads and lightly mottled gray backs and sides. The two species can be distinguished by noting that the white throat of the red-breasted merganser merge imperceptibly with the brown head, whereas the common merganser’s throat is more sharply defined against its reddish-brown head. Female red-breasted mergansers also have a slight protrusion of feathers at the back of their head. The female also has lighter red eyes and feet than the male. They have ash-gray shoulders and a small white patch on the speculum formed by the inner white secondaries, with a black base. The primaries and their coverts are dusky brown.

Both males and females have long, narrow bills with serrated edges, which are bright red in the male and duller in the female.