There has been a decline in breeding numbers since the 1970s - 96 pairs were estimated in 1995 and 80 in 1999. Eutrophication of the waters has reduced the species’ food supply which has resulted in poor productivity and juvenile survival. Mink predation has also had a considerable impact during the breeding season, and incubating females have been most vulnerable. However, in recent decades, it has been suggested that birds may be redistributing to other large lakes in western and central Ireland.
Status: Resident and winter visitor from the Continentto all Irish coasts between October and April.
Conservation Concern: Red-listed due to its declining breeding population. The European population has been evaluated as Secure.
Identification: Medium-sized, plump duck usually seen in large flocks offshore. At closer range, males with yellow knob at base of bill. All dark plumage, with no white on the wing. Males black, females sooty brown with paler cheeks.
Similar Species: Velvet Scoter and other ducks.
Call: Soft piping 'pju'.
Diet: During the summer the diet is varied and includes water plants, insect larvae and freshwater crustaceans. During the winter, they forage mostly in waters less than 20 m deep and with coarse sandy substrates. They feed predominantly on benthic bivalve molluscs.
Breeding: First recorded breeding in Ireland in the beginning of the 20th century at Lower Lough Erne. Numbers increased steadily - up to 150 pairs were estimated during the late 1960s. They nest on islands with dense covering of scrub and tree cover. The breedding population has declined since due to the increase in Mink, which predate the nests and young.
Wintering: Common Scoter are almost entirely marine during the winter, and tend to congregate in large flocks on shallow seas with sandy bottoms supporting their preferred prey.
Where to See: Wexford Bay in County Wexford, Castlemaine Harbour & Rossbehy in County Kerry, Brandon Bay - Inner Brandon Bay in County Kerry, Donegal Bay in County Donegal and the Nanny Estuary & shore in County Meath are among the best wintering sites, supporting 800-4,500 birds.
Monitored by: Irish Wetland Bird Survey.