Parasitic Jaeger 13 



b^ Tail distinctly forked. Xema, p. 21. 



b. Bill long, straight and rather slender ; both mandibles equal. 



a^ Tail short and nearly square ; webs between the toes 



omarginato. Hydrochelidon, p. 24. 



b^ Tail very distinctly forked ; outer feathers elongated and 



pointed ; toes fully wobbed. Sterna, p. 22. 



Family STERCORARIID^. 

 Characters of the only genus. 



Genus STERCORARIUS. 



Bill stout and gull-like with a terminal hook covering the tip of 

 the lower mandible, the basal two-thirds covered by a horny cere 

 which overlaps the nostrils, so that the opening is much reduced ; 

 wings long and strong, outer prunary the longest ; tail with the two 

 centre feathers nxuch jiroduced ; anterior toes fully webbed, hallux 

 small and stmupy. 



Three species on the coasts of the United States. 



Parasitic Jaeger. Stercorarius parasiticus. 



A.O.U. Checklist no 37 — Colorado Records — Ridgway 79, p. 232 ; 

 Drew So, p. IS ; Morrison 89, p. 147 ; H. G. Smith 96, p. 48 ; Cooke 97, 

 p. 50 ; Henderson 03, pp. 234, 109 ; 09, p. 225. 



Description. — Adult — In the sooty form or dark phase the plumage 

 is dark brown throughout, darkest on the mantle, wings and tail; 

 neck with aciuninate rigid feathere streaked with golden straw ; outer 

 jirimaries with white shafts. The light phase has the upper-parts 

 slaty, becoming blackish on the cro\\ni, wings and tail, the throat and 

 under-parts white ; bill brownisli-horn, darkest in front of the cere ; 

 legs black. Length about IS'O ; wing 12*0 ; tail 4-5 ; to end of central 

 feathers SD ; cuhnen 1*3 ; tarsus 1-85. 



Distribution. — The Parasitic Jaeger has a circumpolar range in both 

 hemispheres, breeding in America in Alaska, the Barren Grounds and 

 Greenland, and wandering in the winter to South Africa, New Zealand 

 and portions of South America, chiefly along the coast. It is only 

 occasionally found inland. 



This bird is a rare fall and winter straggler in Colorado. There 

 was an example in Mi's. Maxwell's Museum, taken near Boulder, in 

 December, sometime before 1874 ; H. G. Smith examined a young 

 male in the dark phase, shot on Sloans Lake near Denver in the fall 

 of 1889, and Lowe obtained a third example, now in his collection, 

 on the Arkansas River below Pueblo in the fall of 1894. 



