STERNA. 41 



i/'. "Wing loss than 12.00; occipital feathers short and blended. 



c". Mantle bluish gray, the tail chiefly white; inner webs of quills largely 

 Avhite. (Subgenus Sterna.) 

 d'. Top of head without any black at any season. 



Adult in sitmmcr : Ilead, axillars, lining of wing, and tail- 

 coverts, white, the first with a dusky stripe along each 

 side, entirely surrounding eye, and extending back over 

 ear-covorts ; rest of plumage pale pearl-gray, the quills 

 inclining to silvery white ; bill black in middle portion, the 

 base and tip yellowish. Winter plurnar/e : Similar, but lower 

 parts white ; bill dusky, tipped with yellowish. Length 

 15.00-16.00, wing 9.70-10.60, tail 4.60-6.00 (forked for about 

 1.60-2.60), culmen 1.50-1.70, tarsus .92-.96. Hab. Atlantic 

 coast of South America ; casual on Atlantic coast of United 

 States (New Jersey and Long Island). 



68. S. trudeaui Aud. Trudeau's Tern. 

 (P. Top of head chiefly or entirely uniform black in summer. 

 e". Top of head entirely black in summer. 



/'. Only one web of outer tail-feather entirely white. 



g\ Inner web of outer tail-feather grayish or dusky 

 toward end, the outer web entirely white. Sum- 

 mcr adult: Above pale pearl-gray, lower parts 

 pure white ; entire top of head and nape uniform 

 deep black ; bill (in life) dull orange, dusky at tip , 

 feet fine orange-red. Winter plumage: Similar, 

 but whole top of head white, tinged on occiput 

 and nape with grayish, the side of the head with 

 a dusky stripe surrounding eyes and extending 

 across ear-coverts ; tail shorter and less deeply 

 forked than in summer, the exterior feathers 

 broader and less elongated ; bill duller orange, and 

 feet much less intense red ; bill dusky or dull 

 brownish orange, darker at tip. Young : Similar 

 to winter plumage, but top of head, hind-neck, 

 back, scapulars, tcrtials, and wing-coverts over- 

 laid by a wash of umber-brown, nearlj- uniform on 

 back and crown; sides of head tinged with same; 

 tail-feathers all distinctlj' dusky terminally, especi- 

 ally on inner webs. Downy young : Light brown- 

 ish buff, the breast and belly whitish ; upper parts 

 coarsely and irregularly marbled with black, the 

 sides of the head with a few scattered small mark- 

 ings of the same. Length about 14.00-15.00. wing 

 9.50-10.30. tail 5.00-7.70 (forked for 2.30-5.00). 

 culmen 1.50-1. G5, tarsus .90-1.00. Nc$t of dead 

 6 



