STERCORARIIDjE— the skuas axd jaegers. 217 



S. pomwrmus. Occasionally the middle rectrices are nearly as 

 long and attenuated as in S. longicaudus, 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 (measured 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. parasiticus, 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 S. longicaudus. 

 1 1 is scarcely probable that the two forms are eonspecifie, 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 those of 

 the Pomarine Jaeger (S. pcmarinits), as briefly described on 

 page 214. 



Stercorarius longicaudus Yieill. 



LONG-TAILED JAEGER. 



Popular synonyms. Arctic Jaeger; Buffon's Skua; Long-tailed Skua; Whip-tail (eod- 

 flshermen); Marling-spike (do.). 



Stercorarius longicaudus Vieii/l. Nguv. Diet, xxxii, 1819. 157.— Stejn. Proc. U. S. Nat. 

 Mus. v, 1882, 42— B. B. & R. Water B. N. Am, ii, 1884, 339.— A. O. U. Cluck List. 

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

 Stercorarius longicaudatus De Selys, Faun. Bolg. 1842, 156. 

 Lestris parasitica Ii.lk;. Prodr. 1811, 273 (nee Larus parasiticus Linn.).— Less. Man. 

 ii. 1828. 288— Sw. & Rich. F. B.-A. ii, 1831, 430.— Nutt. Man. ii. 1834, 317. 

 Lestris parasiticus Tkmm. Man. Orn. ed. 1815, 512.— Aud. Orn. Biog. iii. L8S 



Bynop. 1839, 333; B. Am. vii. 1844, 192, pi. 152. 

 Stercorarius parasiticus Saund. P. Z. 8. 1876, 330*.— Ridgw. Nom. X. Am. B. L881. No. 

 699. 

 Larus orepidata Bbbhm & Si hill. Beit. Z. Vog. in. 1822, 212 inec Banes). 

 /., stris buffoni BOH . M ■ ■ < Tasch. iii. 1822, 212.— DeKay. N. Y. Zool. ii. 1844, 315. pi. 133, 

 flg. 291. 

 Stercorarius buffoni CouEB.Proo. Acad. Soi.Phila. 1863. 136; Key, 1872, 309; Cheok List, 

 1873, No. 542; 2d ed. 1882, Xo. 767; B. X. W. (874,615. 

 Stercorarius cepphus Stephens, Bhaw's Gen. Zool. sili.1826, 211,pl. 2S.-rLAWB. In Baird's 



B V Am. 1858,840. Baibd, Cat. \. am. B. 1859, No.655. 

 Lestris microrhynchus Bbi bm, Bandb. Vog. Deutsohl. 1831 

 lessoni Dbol. Mem. ao. R. Lille, 1838, 108. 

 is brachyrhj/nchiu Bbbbm, TogelLlPSE 



—28 



