Shelducks breeding in Ireland and Britain have a well-defined moult migration. Most fly east to the Helgoland Bight in the Waddensea, between late July and early September, where they join birds from Scandinavia and the Baltic. Others remain and moult on North Sea estuaries, such as the Firth of Forth and the Wash.
Status: Resident and winter migrant - Ireland receives additional birds during the winter (October to March) from Scandinavia and the Baltic.
Conservation Concern: Amber-listed in Ireland, as the majority of the wintering population occurs at less than ten sites. The European population is regarded as Secure.
Identification: Medium-sized goose-like duck, mostly white with dark-green head, red bill, a chestnut belt across the breast and black scapulars. Adult males have a prominent knob at the base of the bill.
Similar Species: Only likely to be confused with Red-breasted Merganser and Goosander in Ireland.
Call: Vocal, males in spring with high whizzing whistle, and a disyllabic 'piu-pu'.
Diet: Chief prey source is Hydrobia ulvae, which is present in almost all estuaries, and often in large numbers. Spatial distribution is strongly influenced by the behaviour of this prey, particularly in relation to water depth. They possibly feed at night, detecting prey by tactile clues using their bills.
Breeding: Breeds in open areas along seashores, larger lakes and rivers. Nest in holes in banks, trees, occasionally strawstacks or buildings. There has been a recent expansion in the range of the northwest European population, and birds in Ireland and Britain have been displaced from coastal breeding sites and are increasingly using inland sites.
Wintering: Sheltered estuaries or tidal mudflats.
Where to See: Shelduck have an almost entirely coastal distribution during the winter. Strangford Lough in County Down is the most important site (>3,000 birds). Other important sites include Cork Harbour in County Cork, Shannon & Fergus Estuary in County Clare and Dublin Bay in County Dublin (1,000-2,000 birds).
Monitored by: Irish Wetland Bird Survey (I-WeBS).