FAMILY STEKCOKAKIID^E. SKUAS AND JAEGERS. 33 



FAHILY STERCORARIID^. 



Skuas and Jaegers. 



• 



Nostrils, separate, and not tubular; bill, with cere; front toes, palmate 

 (full webbed); hind toe, small, but always present; end of upper mandible 

 (unguis), swollen, and somewhat rounded; back and wings, 

 always dark, sometimes sooty, sometimes barred with brown ; 

 tail, never white or gray, usually very dark ; middle tail feath- 

 "^ ers, longest. The cere (hard skin=like covering on base of upper 



mandible) will distinguish these birds from Gulls. 



* Group 1. Wing, 11 to 15 inches long. 



Underparts, not entirely pure white; bill, over 1.35; tarsus, over 1.80; middle tail 

 feathers, not pointed ; plumage, sometimes clarji brown; sometimes mixed gray, brown, and 

 white. • Stercorarius pomarimis. Pomarine Jaeger. 



See No. 19. 



Bill, under 1.35; tarsus, under l.SO; middle tail feathers, pointed; base of unguis 

 to frontal feathers less than length of unguis ; shafts of primaries. 3 ellow white. 



Stercorarms longicaudus. Long=tai!ed Jaeger. 



See No. 21. 



Bill, under 1.35; tarsus, under 1.80; middle tail feathers, pointed ; base of unguis to 

 frontal feathers, greater than length of unguis; shafts of primaries, j-ellowish white. 



Stercorarius parasiticus. Parasitic Jaeger. 



See No. 20. 



* Group 2. Wing, over 15 inches long. 



Bill, with cere ; general color, dark brown, more or less streaked with light brown ; a 

 patch of white at base of primaries. Megalestris skua. Skua. 



See No. 18. 



* For directions for measurement, see page 9. 



