8 PACIFIC COAST AVIFAUNA [No. i. 



Stcrcorariiis pomarinus (Temni.). 

 PoMARiNE Jaeger. 



This jaeger was apparently the least common of the three species, and was 

 confined chiefly to the coast regions. I saw it twice in the latter part of June in 

 the Kowak delta, and in July it was frequently seen in the vicinity of Cape Blos- 

 som. An adult male in the light phase of plumage was taken there on July first, 

 '99. The Pomarine Jaeger was also seen at sea between Bering Straits and Kotze- 

 bue Sound. The jaegers select as victims principally the Kitti wakes and Short- 

 billed Gulls. The larger Glaucous and Glaucous-winged Gulls are quite free from 

 the attacks of these robbers. 



Stcrcorarins parasiticus (L,inn.). 

 Parasitic Jaeger. 



I only saw two or three of this species in the vicinity of Cape Blossom, but 

 in the Kowak delta quite a number were noted on the marshy tundras in June. 

 On the twentieth of that month I discovered a nest containing a single egg, incu- 

 bation advanced. The nest was a slight saucer-shaped depression on a low mossy 

 hummock on the tundra. This depression was scatteringly lined with bits of 

 white lichen, such as grew immediately around the nest. The egg is ovate> and 

 measures 2.26x1.70. Its ground-color is olive, over which are scattering spots and 

 lines of sepia and drab. Around the larger end there is a dark wreath of indis- 

 tinct spots, blotches and scrawls of sepia, bistre and drab. This nest was discov- 

 ered by watching the birds, which, by their uneasy flight, betrayed its neighbor- 

 hood. By quietly sitting where I cculd watch the surrounding tundra, the birds 

 finally became accustomed to my presence and one of them, settled down on the 

 nest. Of this pair of Parasitic Jaegers> one was in the dark sooty plumage and the 

 other in the light plumage. As they hovered about> poising against the fresh 

 westerly breeze, the one showing its white breast to the sunlight, and the other in 

 its uniform sombre dress, one could scarcely believe them to be of the same 

 species; and yet here were they mated and breeding. Of this species, those 

 which I saw in June and July were approximately half and half in the light and 

 dark phases of plumage.. 



Stercorariiis longicaudiis (Vie ill.). 

 LoNG-TAiLEi> Jaeger. 



This was the most abundant Jaeger in the Kotzebue reg-ion, and was alike nu- 

 merous alongthe sea-coast and up the Kowak Valley. In the latter locality its arrival 

 was noted on May 22nd. The haunts of these birds were the smooth low-lying 

 tundras, where they would be seen coursing back and forth over the meadows or 

 poising on flnttering wings just like a sparrowhawk, to finally swoop to the 

 ground. Their food appears to be very varied. Aside from the second-handed 

 morsels forced from the gulls, the jaegers prey upon field-mice and insect larvae, 

 as shown by examination of their stomachs. They also appropriate ducks' eggs 

 when the latter are left exposed. Near our first camp at Cape Blossom in July^ 

 there was the carcass of a seal on the beach. This wasalmost constantlv attended 



