Common Eider Somateria mollissima is distributed over the northern coasts of Europe, North America, eastern Siberia and southern Greenland. It breeds in the Arctic and northern temperate regions, but its range expands during winter to as far south as New Jersey, southern Alaska, the western Mediterranean and Kamchatka (Carboneras et al. 2014). It is currently listed as Least Concern, because when last assessed it was not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.
Globally, it has an extremely large range in both the breeding season (>3 million km2) and in winter (>5 million km2), and hence does not approach the thresholds for Vulnerable under the range size criteria (B and D2). Its population size is also extremely large (3.3–4.0 million individuals; Wetlands International 2012), and hence does not approach the thresholds for Vulnerable under the population size criteria (C and D1). Therefore, the only potentially relevant criterion is A, which relates to reductions in population size. Until recently, the population was thought to be declining slowly, but not sufficiently rapidly to approach the threshold for listing as Vulnerable under criterion A (at least a 30% decline over ten years or three generations, whichever is longer).
New data collated from across Europe for the European Red List of Birds (BirdLife International 2015) indicate that the species has declined significantly in recent years, and that this decline is ongoing. A combination of official data reported by 27 EU Member States to the European Commission under Article 12 of the EU Birds Directive and comparable data from other European countries, provided by BirdLife Partners and other leading national ornithologists, suggests that the European population has declined markedly since the end of the last century, and is currently declining overall at a rate of >40% over three generations (27 years, based on a generation length estimated by BirdLife to be 9 years). This corresponds well with the decline evident since the late 1990s in the largest flyway population of S. m. mollissima in the Baltic and Wadden Seas, based both on breeding data (Ekroos et al. 2012) and on midwinter counts conducted as part of the International Waterbird Census (Nagy et al. 2014). Consequently, the species is now classified as Vulnerable at European level (BirdLife International 2015).
Based on the latest population estimates (Wetlands International 2012), Europe (including Greenland) holds >60% of the global population, so the declines in Europe are globally significant. A variety of factors may be driving the decline (Waltho & Coulson 2015), which would have been even steeper if the long-term decline in Greenland not been reversed by a change in harvest regulations in 2001, which allowed the population in part of W Greenland to recover and quintuple in just 11 years (Burnham et al. 2012).
Most of the rest of the global population occurs in North America, for which Bowman et al. (2015) summarise the situation as follows: “Limited available data on the Pacific population S. m. v-nigra [c. 4% of global] suggest that it declined in northern parts of its range between the 1980s and early 2000s; more recently, it has declined in central arctic Canada and NW Alaska, but is stable or increasing elsewhere in Alaska. The data on the American population S. m. dresseri [c. 9% of global] show variable trends, with increases in the north and declines in the south. The trends of the other two populations, Hudson Bay S. m. sedentaria [c. 6% of global] and Northern S. m. borealis [c. 16% of global], are uncertain.”
Given the size of the European population, the magnitude and scale of recent ongoing declines in Europe, and the absence of any evidence of compensatory increases elsewhere in its range, this species appears to qualify for uplisting to at least globally Near Threatened and possibly Vulnerable under criterion A.
Comments on this proposal are welcome, along with any data regarding recent trends in other regions, and any additional information about the threats currently affecting this species across its range.
BirdLife International (2015) European Red List of Birds. Luxembourg: Office for Official Publications of the European Communities. http://www.birdlife.org/datazone/info/euroredlist
Bowman, T. D., Silverman, E. D., Gilliland, S. G., & Leirness, J. B. (2015). Status and trends of North American sea ducks: reinforcing the need for better monitoring. Pp. 1-28 in Savard et al., eds. Ecology and Conservation of North American Sea Ducks. Studies in Avian Biology 46.
Burnham, K. K., Johnson, J. A., Konkel, B., & Burnham, J. L. (2012). Nesting common eider (Somateria mollissima) population quintuples in Northwest Greenland. Arctic, 456-464.
Carboneras, C., Christie, D.A. & Kirwan, G.M. (2014). Common Eider (Somateria mollissima). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. www.hbw.com
Ekroos, J. et al. (2012) Declines amongst breeding Eider Somateria mollissima numbers in the Baltic/Wadden Sea flyway. Ornis Fennica 89: 81-90.
Nagy, S., Flink, S., Langendoen, T. (2014) Waterbird trends 1988-2012: Results of trend analyses of data from the International Waterbird Census in the African-Eurasian Flyway. Wetlands International, Ede. http://www.wetlands.org/Portals/0/TRIM%20Report%202014_10_05.pdf
Waltho, C., & Coulson, J. (2015). The Common Eider. Bloomsbury Publishing.
Wetlands International (2012) Waterbird Population Estimates: 5th edition. wpe.wetlands.org