Red-breasted Merganser

Mergus serrator



This is a diving duck with a slim, long body, about the size of a Mallard. It's part of a group called sawbills. Both sexes have a thin, narrow bill, and a distinctive, wispy, rather shaggy crest on the back of the head. The sexes are otherwise dissimilar; the male has a deep green head, a spotted orange-red breast, grey flanks and a back black. The female's head and nape are reddish-brown, her throat is pale and her neck is grey. Her body plumage is mostly a mixture of greys. The juvenile bird is a dark version of the adult female, but its crest is shorter. When flying, the male displays white sections on the wings with two dark bars, while the female has a smaller white section with only one bar.


It is attracted to lakes and rivers with abundant fish-life; in Britain, it breeds primarily in Scotland, particularly western and central Scotland and the islands and the Highlands. It can also be found in north-west England and north-west Wales, and the west of Ireland. This bird prefers sheltered bays and coastal inlets, as well as areas with woods or cover. During the winter it is almost exclusively a coastal bird.


This bird is usually seen in little, single-sex groups, though larger flocks form in the winter. It sits low in the water when swimming; it dives frequently and dips its head beneath the water searching for something to eat.


The main food of the Red-breasted Merganser is fish such as young salmon and trout, perch, grayling, herring, cod, plaice and sand eel. Diet also includes small crabs, shrimps and aquatic insects. When ducklings first hatch, they eat mostly insects.


When the birds are courting in winter, they make bowing and stretching displays. They make nesting sites on the ground, among roots or bushes, in crevices or between rocks. The female incubates 8-10 eggs for 31 days, and the male deserts during this time. Young depart the nest soon after hatching; they feed themselves but are still cared for by the female for a while. They are independent after 60-65 days, but the female usually leaves before then; a single female or 'auntie' often cares for young birds.


The birds who breed in Britain are mostly resident, although some Red-breasted Mergansers migrate from further north and arrive in Britain and Ireland in late autumn and depart in March. Over 3 400 pairs breed in Britain and Ireland and over winter, individuals may number 9 000 in the UK and over 3 000 in Ireland due to influx from northern Europe.

Observation Tips

Large Scottish rivers and lochs are key spots in the spring; north Wales and the Lake District are active areas too. Coastal areas such as estuaries are the best bet during winter.


Predominately silent, though can make rough croaky, noises, or soft, grunting calls, particularly when displaying and nesting.