King Eider vs Common Eider

In short

The King Eider and Common Eider are both large sea ducks with distinctive male plumages, but they can be differentiated by the King Eider's more pronounced bill knob and colorful head pattern. Females and immatures are more challenging to separate, often requiring close observation of subtle plumage and structural differences.

Identification tips

1. Look for the pronounced bill knob and colorful head of male King Eiders. 2. In mixed flocks, note the flatter, wedge-shaped bill of the Common Eider. 3. Observe habitat: King Eiders are more pelagic in winter, while Common Eiders are often closer to shore. 4. Female and immature eiders require careful observation of plumage patterns and structure.

Size

Both species are similar in size, but the Common Eider is generally bulkier with a slightly longer body.

Plumage

Male King Eiders have a striking orange bill with a large, rounded knob and a multicolored head with a pale blue crown, while male Common Eiders have a more subdued greenish nape and a flatter, wedge-shaped bill. Female and immature eiders of both species are brown and mottled, but King Eiders tend to have a more uniform and darker appearance.

Behaviour

Both species dive for marine invertebrates, but King Eiders are more likely to be seen in mixed flocks with other seabirds during migration. Common Eiders often form large crèches during breeding season.

Habitat

King Eiders winter over a broad area in the Bering Sea, while Common Eiders are more coastal and can be found in both marine and brackish waters. Both species breed in Arctic regions.

Voice

Vocalizations are not a primary distinguishing feature in the field, as both species have similar calls.