The yellow-billed loon is a migratory bird. Solitary pairs breed on lakes in the arctic tundra of the United States, Russia, and Canada from June to September. During the remainder of the year the species winters in more southern coastal waters of the Pacific Ocean and the Norway and North Seas. Non-breeding birds remain in marine waters throughout the year, either in wintering areas or offshore from breeding grounds. The yellow-billed loon (Order Gaviiformes, Family Gaviidae) is one of the largest of the five loon species and similar in appearance to the common loon (Gavia immer). There are no recognized subspecies or geographic variations (American Ornithologists' Union 1998, p. 5). A field characteristic that distinguishes yellow-billed loons from common loons is their larger yellow or ivory-colored bill. Adults weigh 4,000 to 6,000 grams (8.8 to 13.2 pounds) and are 774 to 920 millimeters (30 to 37 inches) in length. Breeding (alternate) plumage of adults of both sexes is black on top with white spots on the wings and underside, and white stripes on the neck. Non-breeding (basic) plumage is gray-brown with fewer and less distinct white spots than breeding plumage, with paler undersides and head, and a blue-gray bill. Hatchlings have dark brown and gray down, and juveniles are gray with a paler head (North 1994, p. 2). Yellow-billed loons are specialized for aquatic foraging with a treamlined shape and legs near the rear of the body, and are unable to take flight from land.