Red-breasted merganser

The red-breasted merganser (Mergus serrator) is a duck species that is native to much of the temperate to subarctic Northern Hemisphere. The red breast that gives the species its common name is only displayed by males in breeding plumage. Individuals fly rapidly, and feed by diving from the surface to pursue aquatic animals underwater, using serrated bills to capture slippery fish. They migrate each year from breeding sites on lakes and rivers to their mostly coastal wintering areas, making them the most frequent species in the genus Mergus to frequent saltwater regularly. The worldwide population of this species is stable, though it is threatened in some areas by habitat loss and other factors.

The adult red-breasted merganser is 51–64 cm (20–25 in) long, has a wingspan of 66–74 cm (26–29 in). Males average slightly larger, weighing 950–1,350 g (34–48 oz), compared to female weight of 800–1,100 g (28–39 oz).

It has a spiky crest and long thin red bill with serrated edges. The male has a dark head with a green sheen, a white neck with a rusty breast, a black back, and white underparts. Adult females have a rusty head and a greyish-brown body. Juveniles look similar to females, but have a shorter crest, and marginally smaller white wing patches.

The range of the red-breasted merganser broadly overlaps with that of the similar and closely related common merganser. The two species can therefore occur in the same place at the same time, though the species often choose different habitats (red-breasted prefers saltwater, common prefers freshwater, but overlap is frequent). Breeding male plumages are fairly distinctive, but other plumages such as those born by females, immatures, and non-breeding males can make the two species hard to distinguish. Female common merganser has more contrast between the darker head and lighter breast, and has a light chin patch not seen on the red-breasted.

During courtship, the female gives a rasping prrak prrak, while the male gives a catlike meow. In flight, the female makes a harsh gruk. At other times this species is largely silent.