Tuesday, November 3, 2015

Surf Scoter

Yesterday, Gerry Hoekstra texted Erika and me that he found six Surf Scoters at Cody Lake in northwestern Rice County. Although three hours passed before we were free to search, we found the birds without difficulty. These ducks were feeding intensely about half-way across the lake (east-west), and, despite their being some distance from the shore, I was able to take these very blown-up photos. My field guides assure me that the field marks of fall Surf Scoters include their vertical (rather than oval) white patches behind their bills and their lack of white wing patches (although these patches are not always visible on swimming birds). Finally, Surf Scoters are less stocky birds and their bill profile is less wedge-shaped than White-wings.
Away from their arctic breeding range, Surf Scoters inhabit the sea coasts of North America. Nevertheless, during migration, these sea ducks are rarely reported everywhere across the United States. In Minnesota, these scoters are uncommon in Lake Superior and rare elsewhere in the state. At sea, Surf Scoters feed on invertebrates, mainly mollusks and crustaceans. Their freshwater diet is less well known, but includes clams, Zebra Mussels, and caddisfly larvae. Anderson et al. (2015) write that they “perhaps rarely [feed] on dense schools of juvenile forage fish.”

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