Friday, August 24, 2012

White-winged vs. Black Scoter

Near the Surf Scoter of the previous post, Erika and I found this male White-winged Scoter. Identification of White-winged Scoters is usually fairly easy--if you can see the white wing patch. That was not the case in the second photo, taken at Sand Lake National Wildlife Refuge near Aberdeen, South Dakota or in the third photo. The white patch was very difficult to discern, and we had to rely on the round shape of the anterior white face patch.
I took the third photo at Lake Oahe several years ago. The bird on the left is a White-winged Scoter, again with the white wing patch not visible. But the shape of the anterior face patch is round, not vertical as in a Surf Scoter. The right bird has a smaller bill and is clearly smaller bodied. Note the white cheeks, This duck is a female Black Scoter.
Black Scoters breed in Alaska and northern Quebec and winter off both coasts of North America. White-winged Scoters have a similar winter range, but breed from Alaska through the Canadian prairies. In Minnesota, the three scoters are "uncommon to rare migrants on Lake Superior, more often in the fall" (Eckert). White-winged Scoters are most often observed. The three scoters are rare fall migrants elsewhere in the state.

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