Somateria mollissima (Linnaeus, 1758)
Family: Anseriformes > Anatidae
This seaduck breeds around the coasts of northern Britain & Ireland, but can be seen further south during the winter months.
British and Irish breeding Eider are at the southern edge of a wider breeding range; while birds breeding further north are migratory, moving thousands of kilometres, our individuals make relatively short movements outside of the breeding season.
Eider feed on Blue Mussels and other molluscs, together with crustaceans and echinoderms. These are taken during dives, typically down to 3 m or so. Individuals favour sheltered feeding and resting sites during the winter, reducing their exposure to the elements.
Select a topic for more facts and statistics about the Eider
Eider identification is usually straightforward.
Listen to example recordings of the main vocalisations of Eider, provided by xeno-canto contributors.
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Status and Trends
Population size and trends and patterns of distribution based on BTO surveys and atlases with data collected by BTO volunteers.
This species can be found on the following statutory and conservation listings and schedules.
The extent of breeding range of the Eider is relatively unchanged since the 1968–72 Breeding Atlas, with gains in occupied 10-km squares Wales, Morecambe Bay and the Isle of Man but some losses in western Scotland and Shetland (Balmer et al. 2013). In Shetland, where the birds are believed to be from the faeroensis subspecies, the has been a strong decline from 17,000 individuals in 1977 to 4,627 in 2012 (Heubeck & Mellor 2013). The population trend elsewhere in the UK is unclear.
|UK winter population||-31% decrease (1995/96 to 2020/21)|
In winter Eiders are found all around the coastline of Britain with the exception of much of the Solway Firth, Cardigan Bay and the Bristol Channel. The greatest concentrations are along the North Sea coast from Shetland to North Yorkshire, and in the northwest in Argyllshire and the Clyde estuary, northern parts of Ireland and Morecambe Bay.
Occupied 10-km squares in UK
|No. occupied in breeding season||500|
|% occupied in breeding season||17|
|No. occupied in winter||685|
|% occupied in winter||23|
European Distribution Map
Since the 1968–72 Breeding Atlas there have been notable breeding distribution gains in northwest Wales, Morecambe Bay, the Isle of Man, and throughout the north coast of Ireland.
Change in occupied 10-km squares in the UK
|% change in range in breeding season (1968–72 to 2008–11)||+5.1%|
|% change in range in winter (1981–84 to 2007–11)||--0.9%|
Eiders are present throughout the year at suitable coastal locations.
Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.
Lifecycle and body size information about Eider, including statistics on nesting, eggs and lifespan based on BTO ringing and nest recording data.
View number ringed each year in the Online Ringing Report
|Maximum Age from Ringing||35 years 6 months 26 days (set in 1994)|
|Typical Lifespan||14 years with breeding typically at 3 year|
|Juvenile Survival||0.33 (in first year)|
|Wing Length||Adults||290.2±14.9 | Range 267–312mm, N=62|
|Males||301.4±9.1 | Range 287–313mm, N=22|
|Females||284±13.8 | Range 255.5–298.5mm, N=40|
|Body Weight||Adults||2.13±0.2 | Range 1.83–2.35kg, N=22|
Feather measurements and photos on featherbase
|Field Codes||2-letter: E. | 5-letter code: EIDER | Euring: 2060|
For information in another language (where available) click on a linked name
Interpretation and scientific publications about Eider from BTO scientists.
Causes of change
The decline of the Shetland population (faeroensis) has been attributed initially to an oil pollution incident in 1978/79 and high levels of unexplained mortality the following winter; the causes of more recent declines are unknown but may include deterrence measures at aquaculture sites and predation by marine mammals including Killer Whales (Heubeck & Mellor 2013). A study in Northumberland identified changes to adult survival as the main driver of population changes, and suggested that this change was caused by food shortages and had led to recent more widespread declines across northern Europe (Coulson 2010). The same study identified very low survival of ducklings and, although this was not identified as the main driver of population change, the author suggested that increasing duckling survival might be the most likely means to reverse the trend for this species.
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