The Parasitic Jaeger 



No. 268 



Parasitic Jaeger 



A. O. U. No. 37. Stercorarius parasiticus (Linnaeus). 



Synonyms. — Richardson's Jaeger. Marlinspike. Gull-hunter. 



Description. — Somewhat similar to preceding species, both in general appearance 

 of plumage and in color phases, the near-adult and common form being merely washed 

 with brownish on sides of breast and across throat, instead of brown-spotted-and- 

 barred. Adult, light phase: Upperparts, lining of wings, sides, flanks, and crissum, 

 grayish sooty brown, blackening on greater coverts, primary coverts, quills, and tail 

 distally, interrupted on hind-neck and cervix by white continuous with underparts, 

 paling on forehead and changing to white at extreme base of bill; remaining under- 

 parts, continuous with broad cervical collar, white, tinged on cheeks, sides of neck, 

 and nape with straw-yellow; primaries whitening on concealed portions of inner webs, 

 their shafts straw-yellow. Bill and cere brownish, blackening on tip; feet and legs 

 black. Adult, dark phase: Entire plumage sooty brownish black, a little paler below 

 (where lighter than in 5. pomarinus). Immature birds are smaller, with central tail- 

 feathers not, or scarcely, projecting, and have chiefly nebulated plumage below, with 

 admixture of pale cinnamon, especially on under tail-coverts, where coarsely barred; 

 the cheeks and neck all around dusky, streaked with whitish and cinnamon-ochraceous. 

 Maturing birds show increasing white, i. e., are more sparingly dusky-streaked or barred 

 below, and in the last stage are merely tinged on throat, nape, and sides of breast with 

 blended dusky. Owing to the habitual cross-breeding of the light and dark phases, 

 the resultant varieties are interminable and their plumage changes hard to follow. 

 Some examples, presumably juvenal of the dark phase, are even heavily washed and 

 skirted with ochraceous-tawny or clay-color — containing a hint of erythrism. In a 

 considerable series of these birds there will be no two specimens alike; but the type 

 showing some degree of nebulated under-plumage will prevail. If all birds were as 

 variable as these, the task of the plumographer would be hopeless. Length 381-533.4 

 (15.00-21.00); av. 431.8 (17.00); wing 330.2 (13.00); tail 190.5 (7.50); bill 30.5 (1.20); 

 tarsus 45.7 (1.80). 



Recognition Marks. — Crow size, but appearing larger; marks much as in 

 preceding species, but central pair of tail-feathers sharply pointed, produced about three 

 inches beyond others (not nearly so long as the Long-tailed Jaeger (S. longicaudus). 



Nesting. — Does not breed in California. Nest: A depression in moss. Eggs: 

 2; light brownish olive to buffy brown, spotted rather sparingly with dark sepia, dark 

 bister, or black, and dull violet-gray. Av. size 58.4x41.9 (2.30 x 1.65). Season: June. 



General Range. — Breeds in high northern latitudes from at least Lat. 8i° 40' 

 south to the Aleutians, central Mackenzie (Great Slave Lake), and Scotland. Winters 

 from the Aleutian Islands, New England, and the coasts of Europe south to Chile, 

 Brazil, Cape of Good Hope, and Australian seas. Many interior records, especially 

 upon the Great Lakes. 



Occurrence in California. — Fairly common migrant, coastwise. Found spar- 

 ingly in winter south of Pt. Conception. 



Authorities. — Cooper (Stercorarius parasiticus), Proc. Calif. Acad. Sci., vol. 

 v., 1874, p. 415 (San Francisco Co.) ; Henshaw, Auk, vol. ii., 1885, p. 232 (Santa Barbara, 

 etc.); Evermann. Auk, vol. iii., 1886, p. 88 (San Buenaventura) ; Grinnell, Pac. Coast 

 Avifauna, no. I, 1900, p. 8 (Cape Blossom, Alaska; desc. nest and eggs, etc.). 



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