214 BIRDS OF ILLINOIS. 



Stercorarius pomarinus (Temm.) 



FOMAEINE JAEGER 



Popular synomyms. Pomarine Skua; Gull-chaser; Gull-hunter; Marling-spike (Newfound- 

 land Banks). 



Larus pomarinus TEMM. Man. Orn. 1815, 514. Sw. & BICH F. B.-A. ii, 1831, 429. NUTT. Man. 



ii. 1831, 315. AUD. Orn. Biog. ill. 1835, 396; Synop. 1839, 332; B. Am. vii, 1844, 186, pL 451. 



Stercorarius pomarinus VTKTT.T.. Nouv. Diet, xxxii, 1819, 158. LAWB. in Baird's B. N. Am. 



1858, 838. BATED. Cat. N. Am. B. 1859. No. 653. B. B. & B. Water B. N. Am. 11, 1884. 332. 



-A. O. U. Check List, 1886. No. 36 -Broow. Man. N. Am. B. 1887. 22. 



Stercorarius pomatorhinus NEWTON. Ibis, 1865, 509. COUES, Key, 1872, 309; Check List, 

 1873, No. 540; ed. 2, 1882. No. 765; B.N. W. 1874, 607. BIDGW. Norn. N. Am. B. 1881. No. 697. 



HAB. Northern portion of northern hemisphere, on the seas and larger inland waters, 

 but chiefly maritime. In winter, south, in North America, to New Jersey, the Great Lakes, 

 Nebraska, etc. ; coast of Peru. 



SP. CHAB. Adult, lightest phase: Pileum, lores, and malar region, with entire upper 

 surface, except the nape, uniform dark sooty slate, with a slight plumbeous tinge in certain 

 lights; anal region and crissum uniform plumbeous- slate, sometimes mixed with whitish. 

 Best of the head and neck (including entire nape), and lower parts, except as described, 

 immaculate white, the auricular region more or less deeply tinged with straw-yellow. Bill 

 brownish white (dull brownish in the dried skin), the terminal third black, sometimes 

 clouded with bluish.* Adult, usual plumage: Similar to the aoove, but chest and nape 

 barred or transversely spotted with dusky, and the sides irregularly barred with the same. 

 Adult, melanotic phase: Entirely dark sooty slate, with ar plumbeous cast in certain lights. 

 Young, light phase: Head, neck, and lower parts dull buff, everywhere barred with dusky ; 

 the bars broad and sharply denned on the crissum and flanks, faint or nearly obsolete on 

 the head and neck. Upper parts brownish dusky, the scapulars and interscapulars tipped 

 with buff, the rump and upper tail-coverts spotted with the same. Young, dark phase: 

 Whole plumage sooty slate, the breast, abdomen, and sides narrowly and rather indis- 

 tinctly, the crissum and upper tail-coverts broadly and sharply, barred with deep buff. 



Total length, about 20.00 inches: extent, 48.00; wing, 13.50-14.00; tail, 8.00-9.00; culmen, 

 1.45-1.75; tarsus, 2.00-2.10; middle toe (without claw), 1.60-1.75. 



In the above diagnosis are described the light and dark 

 extremes of coloration, with an intermediate phase which char- 

 acterizes perhaps a majority of individuals of this species. 

 Scarcely two specimens are exactly alike, however, in the details 

 of coloration, every condition between the light and dark ex- 

 tremes existing in a large series. 



The Pomarine Jaeger is a northern species which doubtless 

 visits Lake Michigan in winter, though the evidence on which it 

 is included as a bird of Illinois is unsatisfactory. In the Bulletin 

 of the Nuttall Ornithological Club, for July, 1876, p. 41, Mr. 



* Adult male. "Bill blackish brown at the end, dingy yellow toward the base; iris 

 brown; tibia, toes, webs, and lower half of tarsus black; the upper half light blue; claws 

 black" (AuDUBON). 



According to MACGELLIVBAT (History of British Birds), the unfeathered parts are 

 colored as follows : "Bill bluish gray, tinged with green, dusky at the end. Feet black; 

 1 he upper half of the tarsus grayish blue. " 



