AVES LARID^E. 1 9 1 



Oilmen, 1.7 inches. 



Tarsus, 0.95 inches. 



Color. Adult (breeding). General color above pearl grey becoming 

 white on the crown and nape ; lower parts pale pearl shading to white on 

 the throat and chin. 



Head : White, with a black streak beginning in front of the eye, which 

 it surrounds, and extending backward over the ear coverts. 



Neck: Pearl grey. 



Back : Mantle pearl grey fading to nearly white on the rump and upper 

 tail coverts. 



Wing : Rather paler than the mantle ; secondaries broadly edged with 

 white, the inner primaries to a lesser degree ; the outer primaries, with 

 the inner webs, pale grey next to the shafts and dark grey on the mar- 

 gins, the "wedges" nearly white. Shafts of quills white. 



Tail : Pale pearl grey, the longer rectrices with silvery white outer webs. 



Lower parts : Pale pearl grey shading into pure white on the throat 

 and chin. 



Bill : Yellow, darkest at the base, shading to lighter toward the tip, and 

 with a black band at the gonys. Tarsi : Orange. Feet : Orange. 



FIG. 115. 



Sterna trudeaui. Young Male, winter. Profile of head. From material in the American 

 Museum. Natural size. 



Adult in autumn and early winter. Similar to breeding birds, except 

 that the band on the side of the head is not so well defined, and has 

 become deep grey instead of black. The feathers in general have a more 

 silvery appearance, this being especially noticeable in the quills which are 

 heavily "frosted" with silvery white. 



