The King Eider
Somateria spectabilis, The King Eider is a large, ornately plumaged duck that spends the predominate portion of its life in the very far north. Its breeding grounds in the Americas are in the Arctic and the North West Territories and it winters mostly no farther south than the Aleutian Islands. In addition it spends the predominate portion of its life out on the remote northern waters and therefore is not easily observable.
The King Eider population migrates very early, sometimes to their own detriment, flying across the tundra in flocks reported at up to 113,000 in one half hour period. Now these birds fly at about 60 km/hr at less than 100 meters off the ground. Imagine yourself on the Arctic tundra with over one hundred thousand birds, flying less than three hundred feet over your head, at forty miles an hour. Wow. And these migrations can fill the sky for hours, ten hours in the case of this particular report.