The White-winged Scoter (Melanitta fusca) is a large sea duck that breeds in northwestern and central North America and winters along both coasts of North America, as well as in Europe and Asia. There are two recognized subspecies of White-winged Scoter:
Melanitta fusca fusca
This subspecies breeds from Alaska across northern Canada to central Quebec. It winters along the Pacific, Atlantic, and Gulf coasts of North America.
Melanitta fusca stejnegeri
This subspecies breeds in eastern Siberia and winters in northeastern Asia along the coasts of Japan, Korea, and China.
There are minor differences in size and plumage between these two subspecies, which has led taxonomists to recognize them as distinct forms of the species. The key identifying features of each subspecies are summarized below.
Distinguishing Features of M. f. fusca
- Breeds in North America
- Winters along all coasts of North America
- Slightly larger in size than M. f. stejnegeri
- Dark brown head and neck
- Blackish brown back and wings
- White secondary feathers form distinct white patch on inner wing when closed
The nominate subspecies M. f. fusca can be distinguished from M. f. stejnegeri primarily based on its larger size and breeding range restricted to North America. The white wing patch also tends to be slightly more extensive in fusca.
Distinguishing Features of M. f. stejnegeri
- Breeds in eastern Siberia
- Winters along Asian coasts
- Slightly smaller in size than M. f. fusca
- Dark brown head and neck
- Blackish brown back and wings
- White secondary feathers form distinct but smaller white patch on inner wing when closed
The subspecies M. f. stejnegeri is smaller and has a more restricted breeding and wintering range than fusca. The white wing patch also tends to be slightly smaller in stejnegeri.
Geographic Ranges
The breeding and wintering ranges of the two White-winged Scoter subspecies can be summarized as follows:
Breeding Ranges
Subspecies | Breeding Range |
---|---|
M. f. fusca | Alaska across northern Canada to central Quebec |
M. f. stejnegeri | Eastern Siberia |
Wintering Ranges
Subspecies | Wintering Range |
---|---|
M. f. fusca | Pacific, Atlantic, and Gulf coasts of North America |
M. f. stejnegeri | Coasts of northeastern Asia, including Japan, Korea, and China |
As the tables illustrate, M. f. fusca breeds across northern North America and winters along both the Pacific and Atlantic coasts of the continent. M. f. stejnegeri has a more restricted range, breeding only in eastern Siberia and wintering along the Asian coast.
plumage and Size Differences
Although the two subspecies are very similar in overall appearance, some minor differences in plumage and size have been noted:
- M. f. fusca is slightly larger than M. f. stejnegeri
- The white wing patch is more extensive in M. f. fusca
- M. f. stejnegeri has a smaller white wing patch
- Plumage colors are nearly identical between the two forms
These subtle differences reflect the geographic separation and genetic divergence between these subspecies over time. However, the overall plumage pattern remains fundamentally the same in both subspecies.
Taxonomic Treatment
The White-winged Scoter was first scientifically described in 1816 by the German naturalist Johann Friedrich von Brandt. The type specimen originated from the Kamchatka Peninsula region of far eastern Russia.
In 1874, Leonhard Hess Stejneger described a different form of White-winged Scoter collected from the Commander Islands in the western Bering Sea. This was designated Melanitta fusca stejnegeri and represented the Asian form of the species. For many years this was considered a separate species from the North American M. f. fusca.
By the early 20th century, most taxonomists recognized stejnegeri as a subspecies of the widespread White-winged Scoter M. fusca. This treatment as conspecific subspecies has been adopted in modern taxonomic authorities, including the American Ornithologists’ Union.
Both subspecies M. f. fusca and M. f. stejnegeri are considered to belong to the same polytypic species Melanitta fusca. However, some subtle geographic variation in size and plumage has led to them being recognized as distinct subspecies.
Evolutionary Relationships
The White-winged Scoter belongs to the genus Melanitta in the family Anatidae (ducks, geese, and swans). Its closest evolutionary relatives are the other two scoter species:
- Black Scoter (Melanitta americana)
- Surf Scoter (Melanitta perspicillata)
These species collectively make up the scoter clade within the seaduck tribe Mergini. Scoters are adapted for diving to feed on mollusks, crustaceans, and other bottom-dwelling prey. Their stocky bodies, large bills, and dark coloration are signatures of this lifestyle.
The ancestor of today’s White-winged Scoter likely diverged from the ancestors of Black and Surf Scoters during the late Pliocene or early Pleistocene epochs. Subsequent isolation between populations in Asia and North America likely led to the divergence between subspecies stejnegeri and fusca.
Ongoing gene flow between some populations of the two subspecies where their ranges overlap may be preventing more definitive differentiation. However, the distinct breeding ranges and subtle morphological differences support their current taxonomic status as subspecies. More molecular genetic research may help shed light on the evolutionary divergence within the species.
Summary and Conclusion
- The White-winged Scoter has two recognized subspecies:
- M. f. fusca – breeds in North America, winters along North American coasts
- M. f. stejnegeri – breeds in Siberia, winters along Asian coasts
- The subspecies differ subtly in size (fusca larger) and extent of the white wing patch (more extensive in fusca)
- Both forms were originally described as separate species, but are now considered subspecies of the polytypic M. fusca
- The White-winged Scoter evolved from other scoter species during the Pliocene/Pleistocene
- Isolation between Asia and North America populations likely led to divergence into subspecies stejnegeri and fusca
In conclusion, there are two distinct subspecies of the White-winged Scoter that can be differentiated by subtle size and plumage details as well as their geographic breeding and wintering ranges. More research may continue to elucidate the evolutionary history of these subspecies and their degree of reproductive isolation from one another. But currently, the consensus of taxonomic authorities is to recognize these as subspecies M. f. fusca and M. f. stejnegeri of the single polytypic species Melanitta fusca.