STERCORARIID.E— THE SKUAS AND JAEGERS. 217 



S. ponmrhim. Occasionally the middle rectrices are nearly as 

 long and attenuated as in ^S". l<yn<jlcaudm, and in the plumage 

 there is sometimes hardly any difference between examples of 

 the two species. They differ constantly, however, in the form 

 of the bill and, in adult birds, in the color of the tarsi; a bird 

 with black tarsi and having the nasal shield (measuied along 

 the culmen) decidedly longer than the terminal portion of the 

 bill (from the point to the anterior edge of the nostril) being 

 with certainty ^S". jxinmitwiis, while an example in adult plumage 

 having pale bluish tarsi and the nasal shield not longer than 

 the terminal portion of the bill, is sure to be 8. hngicaudus. 

 It is scarcely probable that the two forms are conspecific, but 

 possibly they may interbreed to a slight extent, and thus pro- 

 duce hybrids. 



The Parasitic Jaeger is known as an Illinois bird only on ac- 

 count of its occasional occurrence on Lake Michigan during 

 winter. Its habits are not obviously different from tho.se of 

 the Pomarine Jaeger {S. poT/iarinus), as briefly described on 

 page 214. 



Stercorarius long-icaudus Yieill. 



LONG-TAILED JAEGES. 



Popular synonyms. Arctic Jaeger: Buffons Skua; Long-tailed Skua; Whip-tail (cod- 

 fishermen); Marling-ppike (do.). 



Stercorarius longicaudua Vieill. Nouv. Diet, xxxii, 1819. 157.— Stejk. Proc. U. 8. Nat. 



Mus. V, 18S2, 42.— B. B. <fe R. Water B. N. Am, ii. 1884, 339.— A. O. U. Check List, 



1886, No. 38.— RiDGW. Man. N. Am. B. 1887, 23. 

 Stercorarius longicaudatus De Selts, Faun. Belg. 1842, 156. 

 Lestris parasitica Illiq. Prodr. 1811, 273 (nee Lams parasiticus LiNN.).— Less. Man. 



ii, 1328. 2.S8.— Sw. & Rich. F. B.-A. il, 1831, 430.— Nutt. Man. ii. 1834. 317. 

 Lestris parasiticus Tkmm. Man. Orn. ed. 1815, 512.— Aud. Orn. Biog. iii, 1835, 470, 



Synop. 1839, 333; B. Am. vii. 1844, 192, pi. 452. 

 Stercorarius parasiticus Saund. P. Z. S. 187C, 330.— Ridgw. Nom. N. Am. B. 1881. No. 



699. 

 Larus crepidata Bbehm & Schill. Beit. Z. Vog. iii, 1822, 212 inec Baxks). 

 Lestris huffoni Boie. Meyer's Tasch. ill, 1822, 212.-DeKay. N. Y. ZooI. ii, 1844, 315. pi. 133, 



flg. 291. 

 Stercorarius huffoni CouES. Proc. Acad. Sci. Phlla. 18G3, 136; Key, 1872. 309; Check List. 



1873, No. 542; 2d od. 1&82. No. 767; B. N. W. 1874.615. 

 Stercorarius cepvhus Stephens, Shaw's Gen. Zool. xiii,1826, 211, pL 23.— Lawe. in Baird'a 



B. N. Am. 1858. 810.— Baied, Cat. N. Am. B. 1859, No. 655. 

 Lestris microrhynckus Beehm. Handb. Vog. Deutschl. 1831.725. 

 Lestri* lessoni DEaL. Mem. Ac. R. Lille, 1838,108. 

 Lestris hrachyrliynchus Bbehm. Vogelf, 1855,337, 



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