The eider is a large sea duck that is found in northern regions around the world. There has been some confusion over whether the eider should be classified as a duck or a goose. This article will examine the evidence and provide a definitive answer to the question: is the eider a duck or a goose?
In the opening paragraphs, it’s important to provide a quick answer to the main question. So to directly answer – the eider is considered a duck, even though it has some goose-like qualities. The eider belongs to the genus Somateria which is grouped under the duck subfamily Anatinae in the family Anatidae. Anatidae includes ducks, geese, and swans. So taxonomically, the eider is classified as a duck.
Characteristics of the Eider
The eider is a large waterfowl, weighing 2-3 kg with a length of 50-71 cm. It spends most of its life floating on the ocean, only coming on land to breed. Here are some of the key characteristics of eiders:
Appearance
– Stocky body shape similar to a goose
– Broad rounded head and short thick neck
– Wingspan of 80-110 cm
– Males are black and white in coloration
– Females are brown with black barring
Behavior
– Excellent divers and swim underwater to feed
– Form large flocks on the ocean in winter
– Nest on ground on offshore islands in colonies
– Males do not participate in rearing young
– Very sociable, synchronize breeding and migrations
Habitat and Range
– Circumpolar distribution in northern regions
– Found along Atlantic, Arctic, and Pacific coasts
– Four recognized species of eider ducks
– Prefer cold marine habitats and nest on islands
So in terms of appearance, the eider looks more like a goose than a typical duck. However, its diving behavior, ground nesting, and solitary male habits are characteristic of ducks. The eider seems to display a mix of duck-like and goose-like qualities.
Taxonomic Classification of the Eider
To definitively determine whether the eider is a duck or goose, we need to look at its scientific classification:
Taxonomic Rank | Classification |
---|---|
Kingdom | Animalia |
Phylum | Chordata |
Class | Aves |
Order | Anseriformes |
Family | Anatidae |
Subfamily | Anatinae |
Genus | Somateria |
Species | S. mollissima, S. spectabilis, S. fischeri, S. stelleri (4 recognized species) |
This classification shows that eiders belong to the family Anatidae which includes all ducks, geese, and swans. Within Anatidae, the eider is grouped under the subfamily Anatinae which contains only ducks. Finally, eiders are classified in their own genus Somateria.
So taxonomically, eiders are considered ducks, not geese. This definitive classification solves the confusion over whether the eider should be characterized as a duck or goose.
Differences Between Ducks and Geese
Beyond the taxonomy, there are some general biological differences between ducks and geese:
Characteristic | Ducks | Geese |
---|---|---|
Body size | Small to medium | Large |
Neck | Long, slender | Short, thick |
Legs | Set further back on body | Set closer to center of body |
Migration | Long distance | Short distance |
Molting | Replace all flight feathers simultaneously, cannot fly during molt | Replace primaries one at a time, can still fly during molt |
Based on these differences, the eider aligns more closely with features typical of ducks rather than geese. The eider has a long slender neck, legs set further back on the body, and molts all its flight feathers simultaneously.
Evidence the Eider is a Duck
Let’s review the key evidence that the eider should be considered a species of duck:
Taxonomic Classification
– Placed in subfamily Anatinae which only contains ducks
– Classified in genus Somateria along with other duck species
Physical Features
– Long, slender neck unlike a goose’s short neck
– Legs positioned further back like other diving ducks
– Dense layer of down feathers used for insulation
Behaviors
– Excellent underwater diving ability using wings for propulsion
– Male abandons female after mating and does not help rear young, typical of ducks
– Forms large flocks in winter, safety in numbers
– Nests in large colonies on ground or cliff ledges near water
Habitat Preference
– Marine habitats, coastal waters, bays, and inlets
– Northern coastal regions with cold water
Diet
– Mollusks, crustaceans, echinoderms, fish, aquatic insects
– Forages underwater for food sources like other diving ducks
Overall, the eider matches ducks rather than geese in its taxonomy, physical attributes, behavior patterns, habitat preferences, and diet. These key factors provide convincing evidence that the eider should be classified as member of the duck family.
Evolutionary Relationship to Ducks and Geese
The evolutionary history of the eider also supports its position within the duck family. The order Anseriformes which contains all ducks, geese, and swans originated in the Cretaceous period about 80-90 million years ago. Early on, the evolutionary paths of geese and ducks diverged into separate branches.
Eiders belong to the genus Somateria which is estimated to have split from the genus Anas around 23 million years ago in the Miocene epoch. Anas contains the typical duck species like the mallard and pintail. So the lineage leading to eiders separated from other ducks quite a long time ago. However, eiders still maintained an evolutionary relationship to ducks rather than converging with geese.
Based on this evolutionary history, the eider’s ancestry traces back to early diving ducks. The eider lineage adapted to marine environments and colder regions over millions of years. But taxonomically and genetically, the eider remains allied with other ducks in the Anatinae subfamily.
Unique Adaptations of the Eider
While the eider is indeed a duck, it has developed some unique adaptations that allow it to thrive in harsh northern marine environments:
Dense Down Feathers
Eiders have an inner layer of soft, fluffy down feathers that are tightly packed and provide excellent insulation against cold air and water. The down is so dense that it was historically used to fill pillows – giving rise to the name ‘eiderdown’.
Salt Glands
Since they feed in saltwater areas, eiders have specialized salt glands located above the eyes that remove excess sodium chloride from their bloodstream.
Nest Formation
Female eiders pluck down feathers from their own breasts to line the nest. This provides superb insulation that keeps eggs warm in cold climates.
Foraging Adaptations
Eiders have serrated edges on their bill that help grip slippery mollusks and crustaceans. Their wings provide propulsion for diving and swimming underwater to depths over 20 m while foraging.
Cold Temperature Tolerance
With excellent insulation from down feathers, dense body fat, and an efficient circulation system, eiders can withstand extremely cold air and water temperatures.
These adaptations have allowed the eider duck to flourish in the challenging marine environments of northern latitudes. Their evolutionary relationship to other ducks is clear, even though they have developed specialized features for their habitat.
Species of Eiders
There are four recognized species of eider ducks found in different regions:
Common Eider (Somateria mollissima)
The largest and most widespread eider species. Breeds across northern regions of Europe, Asia, eastern North America, and Greenland.
King Eider (Somateria spectabilis)
Native to northern latitudes of North America and Russia. The male has brightly colored yellow, blue, and orange patches on its head.
Spectacled Eider (Somateria fischeri)
Named for the large white eye patches on the male. Breeds in coastal eastern Siberia and winters in shallow waters of the Bering Sea.
Steller’s Eider (Polysticta stelleri)
Smallest eider species, named after German naturalist Georg Wilhelm Steller. Breeds in Arctic eastern Siberia and Alaska.
Despite some habitat and appearance differences, all four eider species share the same duck-like qualities and are aligned taxonomically. There are no separate goose-like eider species.
Relationship to Extinct Ducks
The fossil record also confirms the eider’s relationship to other seaducks within Anatidae. Extinct species like Chendytes and Hadornis were large diving ducks that lived during the Miocene and Pliocene.
They had similar body plans to the eiders, with goose-like proportions but duck-like features. These ancient ducks were likely transitional species linking typical ducks to the modern eiders.
So paleontology further supports the theory that eiders originated from ancient seaducks and are rightly classified as ducks. They do not represent an intermediate form between geese and ducks.
Conclusion
In summary, the preponderance of evidence definitively shows that the eider should be categorized as a duck, not a goose:
– Taxonomically classified within the duck subfamily Anatinae
– Physical features like long neck and hind-positioned legs are duck-like
– Behaviors such as solitary male habits and diving for food are characteristic of ducks
– Evolutionary history traces to early diving duck lineages, not to geese
– Adaptations like down insulation and salt glands help survive northern marine environments
– Extinct transitional species link modern eiders to ancient seaducks
While the eider has some superficial goose-like qualities, its anatomy, genetics, evolution, behavior, and ecology align with duck characteristics. So the eider properly belongs to the family Anatidae as a marine duck superbly adapted to northern latitudes, not as an intermediate goose-duck. After examining all the evidence, the eider clearly deserves classification as a distinct duck species, not a goose.