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Scoters abound on Juneau waters

Posted: Sunday, May 25, 2008

Enormous rafts of black seaducks have congregated in Gastineau Channel in recent weeks, diving in sequence like falling dominoes. These are scoters, and there have been thousands of birds in some of the large rafts.

Photo Courtesy Of Riley Woodford
Photo Courtesy Of Riley Woodford

Their synchronous diving is entertaining. Within a few seconds, as if cued by some secret signal, dozens or even hundreds of ducks plunge beneath the water. In a large flock, one edge dives first, and row after row of ducks disappears. About 20 or 30 seconds later, they pop up, and in the course of five or 10 seconds the entire flock reappears.

It's often apparent the scoters are eating blue mussels. With binoculars you can sometimes see a scoter repositioning a big mussel in its beak in order to swallow it. Scoters mainly eat mussels and other shellfish, including small crabs. The scoter has a gizzard like a powerful fist that crushes mussels and grinds up the shells. This organ can crush a clamshell that would require a hammer for us to break open.

Scoters also eat herring roe, and the herring spawn in Berners Bay and Lynn Canal earlier this month drew large flocks of scoters. In summer, when scoters are nesting on freshwater lakes, they feed mostly on aquatic insects, and some water plants such as pondweed.

Scoters nest on freshwater, mostly in the Arctic, in northern Alaska and Canada. Nonbreeding scoters such as juveniles may not migrate to the breeding grounds. Scoter ducklings are precocious and born ready to swim and feed; they can catch bugs and don't need to be fed like many baby birds. Scoter broods will often mix, and one parent may be seen with large numbers of ducklings. They grow quickly and in about three months they're ready to migrate south with their parents.

There are three kinds of scoters; in Southeast Alaska surf scoters are by far the most abundant, white-winged scoters are somewhat common and black scoters are least common. All are similar at a glance - large black ducks generally in big flocks. Those flocks may contain a mix of the three species.

Binoculars really enhance scoter-watching - their feeding, their diving behavior, and especially their striking faces.

These ducks have an oversize, knobby bill. Close up, the male surf scoter is colorful, with a bright orange, white and black bill, and a distinct white patch on the back of the neck and on the forehead. As the name implies, white-winged scoters have an obvious white patch on the wings, males also have a striking white stripe under the eye. Black scoters are all black.

Surf scoters and white-winged scoters don't tend to vocalize, but black scoters will call with a clear whistle. That's not to say scoters are quiet, though, there's usually a fair amount of splashing as they feed, and their wings make a whistling sound as they fly. These big ducks don't leap into flight like mallards, they need some "runway" space on the water to get going, and their wings slap against the surface as they gain the speed to get fully airborne. Once aloft they are powerful fliers and cover hundreds of miles in just a few days during migration.

In the late 1990s, biologists tagged 22 white-winged scoters with tracking transmitters in Prince William Sound. The birds used three widely separated breeding areas within the boreal forests of western Canada and Alaska. One nested in the Yukon Flats National Wildlife Refuge north of Fairbanks in Interior Alaska; two nested in the Old Crow Flats, in the Yukon Territory; and 13 nested in the Mackenzie, Anderson and Horton River basins in Canada's Northwest Territories.

In February 2001, a female white-winged scoter was caught in Auke Bay and equipped with a transmitter. In May she flew about a 1,000 miles due north and nested about 150 miles east of the McKenzie River Delta in the Canadian Arctic. She returned to Southeast Alaska in early August.

Last summer researchers captured and banded scoters in Seymour Canal about 30 miles south of Juneau. Like all waterfowl, scoters go through a brief period in summer when they molt their feathers and are temporarily flightless, and this is advantageous for duck-catching biologists. A female white-winged scoter was captured already wearing a band. Reports indicated she was originally banded as a young-of-the-year in August 2003 at Redberry lake in Central Saskatchewan, and she had been recaptured there as an adult in 2006. That's about 1,100 miles east of Prince Rupert.

Scoters are commonly called coots on the East Coast, and surf scoters are known as skunk-head coots because of the black and white markings (These are not to be confused with the "real" coot, a duck-like bird in the rail family). Back east, white-winged scoters can form winter flocks numbering tens of thousands of birds; a raft of 180,000 scoters was counted off Long Island, New York, on as December day in 1952.

For more on Alaska's tagged scoters, see: http://www.wildlife.alaska.gov/index.cfm?adfg=waterfowl.surfscotermap.

• Riley Woodford is the editor of the Alaska Department of Fish and Game's online magazine, Alaska Fish and Wildlife News, and produces the Sounds Wild radio program.



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