KEY TO FAMILIES. - WATEll BIi;i. 



13 



Nostrils, separate not tubular; bill, with cere (a horny or skin-like covering on base of 

 upper mandible) ; bind toe, sometimes very small; end of upper mandible (uuguis), swollen 

 and somewhat rounded; back an 1 wings, always dark, sometimes sooty, sometimes barred 

 with brown; tail, never white or gray, usimllv very dark; middle tail feathers, longest, 





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but only very long in adult birds, sometimes only slightly longer than rest of tail feathers in 

 immature birds; in brown plumages, the axillars (feathers extending from armpit) are 

 heavily barred, brown and white; in other plumages, the axillars and under wing coverts are 

 sooty brown or dark slaty brown. Family STERCORARIID/E. Skuas and Jaegers. 



See page 34. 



Nostrils, separate not tubular; bill, without cere ; bind toe, sometimes very small; upper 

 mandible, curved; uuguis (end of bill), not swollen; middle tail feathers, about equal in 

 length to the others; tail, rarely dark, although sometimes tipped with black or brown; 

 axillars and under wing coverts, white or gray, sometimes with narrow gray lines or faint 

 wavy bars. 



Family LARID/E. Subfamily LARIN/E. Gulls. 



See page 36. 



43 



Nostrils, separate not tubular ; hind toe, sometimes very small ; upper mandible, nearly 

 straight, not hooked or decidedly rounded near tip; outer tail feathers, usually longer than 

 middle feathers. Family LARID^E. Subfamily STERNIN^E. Terns. 



See page 41. 



Bill, like blade of a knife, the under inaudible the longer; plumage, black above, white 

 below. Family RHYNCHOPID/E. Skimmers. 



See page 45. 



