L ARID^E CXXVIII. 219 



329. STERCORARIUS Brisson. (Lat, scavenger.) 



643. S. pomarinus (Temminck). POMARINE JAEGER. Chiefly 

 blackish, colors varying with age; middle tail feathers broad to 

 the tip, projecting about 4 inches. L. 20. W. 15. T. 9. B. l. 

 Arctic, S. in winter to N. J. (Eu.) (TTCO/ZO, flap ; pis, nose.) 



644. S. parasiticus (L.). PARASITIC JAEGER. Dark brown; 

 middle tail feathers acuminate, projecting 4 inches. L. 20. W. 

 13. T. 5. B. 1J. Arctic, S. in winter to N". Y. (#w.) 



645. S. longicaudus (Vieillot). LONG-TAILED JAEGER. Sooty 

 black; tail feathers filamentous, projecting 8 or 10 inches. L. 22. 

 W. 12. T. 13. B. l. Arctic, S. in winter. (Eu.) 



FAMILY CXXYIII. LARID-ffi. (THE GULLS.) 



Long-winged swimmers, with the nostrils not tubular. Bill usu- 

 ally long, horny, not serrate nor lamellate ; nostrils developed ; no 

 gular pouch. Feet palmate ; tibia feathered ; legs near centre of 

 equilibrium ; hind toe elevated, small, often wanting. Wings very 

 long and pointed. Tail well developed. General color usually 

 white, with a darker mantle of a pearly bluish tint, and commonly 

 with some black markings. Sexes alike in color, but the plumage 

 varying much with age and season. Genera about 12; species 90 ; 

 abounding about all large bodies of water, and of remarkable 

 power of flight. Altricial; food chiefly fishes. 



a. Bill more or less hooked ; (general color chiefly white, with a darker, 

 bluish, grayish, or slaty mantle) ; gulls. (Larince.) 



b. Tarsus rough or serrate behind ; tail even GAVIA, 330. 



bb. Tarsus nearly entire behind. 

 c. Hind toe rudimentary or wanting, with minute claw or none; tail 



slightly emarginate RISSA, 331. 



cc. Hind toe small, but with a perfect claw. 



d. Tail even LARUS, 332. 



dd. Tail forked XEMA, 333. 



aa. Bill not hooked, the mandibles even; tail deeply forked (in our species). 



(Sternince.) 



e. Tail much more than | wing, its outer feathers narrow and pointed; toes 

 well webbed. (Color chiefly white, with a black cap in full plumage, 

 and the quills dusky with a long white stripe.) 



f. Bill stout, its depth at base equal to J culmen. GELOCHELIDON, 334. 



ff. Bill slender, its depth at base not \ its length. . . . STERNA, 335. 



ee. Tail little more than J wing, its outer feathers broad and rounded; 



toes scant-webbed; colors dark HYDROCHELIDON, 336. 



330. GAVIA Boie. 



646. G. alba (Gunner). IVORY GULL. Adults pure white; 

 young spotted; feet black. L. 16 to 20. W. 13. B. l. Arctic, 

 rarely to U. S., in winter. (.?.) 



