|The Skuas of the North American Pacific coast|In: The Auk: a quarterly journal of ornithology. The American Ornithologists' Union: Washington, D.C.. ISSN 0004-8038; e-ISSN 1938-4254, meer
The characters of the six commonly recognized forms of skuas, belonging to the three species Catharacta skua, C. chilensis, and C. maccormicki are outlined briefly. Particular attention is given to the South Polar Skua, its color phases, juvenal plumage, annual cycle, and identification. The occurrence of this species along the Pacific coast of North America as an uncommon but regular fall visitor to both California and Washington is documented; no valid evidence suggests that any other form has occurred. Thus C. (skua) chilensis, C. s. lonnbergi, and C. s. antarctica should be removed from the North American list and C. maccormicki added. The South Polar Skua is a regular transequatorial migrant in the Pacific; the movement perhaps includes mostly immatures. Some evidence suggests that this migration takes the shape of a clockwise loop in the North Pacific. Regular occurrence of the species in other seas of the Northern Hemisphere has not yet been well documented, but records exist for both the North Indian and North Atlantic oceans.