18 JAEGERS 



KEY TO SPECIES OF STERCOKARIUS. 



1, Middle pair of tail feathers wide, and rounded at ends. 



pomarinus, p. 18. 

 r. Middle pair of tail feathers narrow and sharp-pointed. 

 2. Middle feathers about half longer than rest of tail. 



parasiticus, p. 18. 

 2'. Middle feathers about twice as long- as rest of tail. 



longicaudus, p. 18. 



36. Stercorarius pomarinus (Temm.). Pomarine Jaeger. 



Adults- — Light phase : face, crown, and upper parts, except collar, sooty 

 black ; throat white, becoming- silky yellow on cheeks and around back of 

 neck ; breast white, chest and sides mottled with sooty. Dark jjhase : wholly 

 dark sooty or phimbeous- All grades are found between the dark and 

 light phases. Young : back dusky, feathers tipped with buff ; rest f)f 

 plumage dull buff, barred with dusky. Length: 20-23, wing 13.50-14.00, 

 tail 8-9, bill 1.45-1.75. 



Distribution. — Northern part of northern hemisphere ; south in winter to 

 Africa, Australia, and probably South America ; in the United States to 

 Michigan, Nebraska, and California. 



Mr. Nelson found the pomarine jaeger largely replacing the other 

 two jaegers along the shores of the Arctic Ocean, especially on the 

 edge of the ice pack and abont the whaling fleet, where it found 

 abundant fare. He says that the peculiar twist of its long tail 

 feathers makes it conspicuous and easily identified as far as seen. 

 When feeding it gives a low, harsh, chattering cry. 



Compared with the parasitic jaeger, the pomarine is a clumsy 

 cowardly bird, Mr. Nelson tells us, and is made the sport of its active 

 little relative. When met in the air, the pomarine wards off attack 

 from one side by a half-closed wing, and from above by raising both 

 wings to form an arched shield over its back. One that Mr. Nelson 

 saw attacked alighted on the river, and "at every swoop of its 

 assailant thrust its head under water, exhibiting the most ludicrous 

 terror. " 



37. Stercorarius parasiticus (Linn.). Parasitic Jaeger. 

 Adults. — Light phase : upper parts slaty, becoming blackish on crown, 



wings, and tail ; throat and under parts white ; sides of head and neck 

 white or grayish, tinged with yellow. Dark phase : entire plumage slaty 

 or sooty, darkest on crown, wings, and tail. Young: head and neck 

 streaked, and under parts spotted and barred with buff and dusky. Length : 

 15.50-21.0:), wing 12.67, tail 4.90-6.25, bill 1.27. 



Distribution. — Northern part of northern hemisphere, breeding in arc- 

 tic regions ; south in winter to New York, Illinois, Colorado, and southern 

 California. 



Nest. — A depression in the moss. Eggs : 2. 



38. Stercorarius longicaudus Vieill. Long-tailed Jaeger. 

 Adults.— Top and sides of head black ; back slaty ; neck and lower parts 



