The king eider (Somateria spectabilis) and the common eider (Somateria mollissima) are two closely related species of sea ducks. Both species are found in the Arctic and subarctic regions of the Northern Hemisphere. However, the king eider is primarily a marine bird, while the common eider is more of a coastal bird.
King eiders are generally larger than common eiders, with males weighing up to 3.5 pounds and females weighing up to 2.5 pounds. Common eiders, on the other hand, typically weigh between 2 and 3 pounds. Both species have black and white plumage, but the king eider has a more distinctive black and white pattern on its head and neck. King eiders also have a larger, more colorful bill than common eiders.