Unlike other loons/divers, this bird may migrate in flocks. It winters at sea, mainly on the Pacific coast, or on large lakes over a much wider range, including China, Japan, North Korea, South Korea, United States and Mexico. It has occurred as a vagrant to Greenland, Hong Kong, Great Britain, Spain, Finland and Switzerland (Dec 2015).
Breeding adults are like a smaller sleeker version of great northern diver/common loon. They measure 58–74 cm (23–29 in) in length, 110–128 cm (43–50 in) in wingspan and weigh 1–2.5 kg (2.2–5.5 lb). They have a grey head, black throat, white underparts and chequered black-and-white mantle. Non-breeding plumage is drabber with the chin and foreneck white. Its bill is grey or whitish and dagger-shaped. In all plumages, lack of a white flank patch distinguishes this species from the otherwise very similar black-throated diver/Arctic loon.
The call is a yodelling high-pitched wailing, as well as harsh growls and barks.
Habitat and range
The Pacific loon breeds on tundra lakes, and winters in the open ocean or other large bodies of water. It breeds primarily in northern Canada and eastern Siberia, and winters along the Pacific coast of North America.
- BirdLife International (2012). "Gavia pacifica". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
- "Pacific Loon Spotted on Finnish Lake". YLE.fi. Yleisradio Oy. November 16, 2010. Retrieved January 29, 2011.
-  (2011).
- Peterson, Roger Tory (2002). A Field Guide to the Birds of Eastern and Central North America (5 ed.). New York, NY, USA: Houghton Mifflin Harcourt. p. 9. ISBN 978-0-395-74047-7.
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The following articles deal with separation of Pacific diver/Pacific loon from black-throated diver/Arctic loon:
- Birch, A. and Lee, C-T, 1997, Field identification of Arctic and Pacific Loons, Birding 29: 106-115.
- Birch, A and Lee, C-T, 1995, Identification of the Pacific Diver - a potential vagrant to Europe, Birding World 8: 458-466.
- Harrison, Peter (1988). Seabirds: An Identification Guide. London: Christopher Helm. ISBN 0-7470-1410-8