STERNA. 41 



U^. Wing less than 12.00 ; occipital feathers short and blended. 



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

 white. (Subgenus Sterna.) 

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



Adult in summer : Head, 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-coverts ; rest of plumage pale pearl-gray, the quills 

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

 base and tip yellowish. Winter plumage : Similar, but lower 

 parts white ; bill dusky, tij^ped 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). 



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

 d'^. Top of head chiefly or entirely uniform black in summer. 

 e\ Top of head entirely black in summer. 



p. 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. Smn- 

 mer adult : Above pale pearl-gray, lower parts 

 pure white ; entire toj) 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, tertials, and wing-coverts over- 

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

 back and crown ; sides of head tinged with same; 

 tail-feathers all distinctly dusky terminally, especi- 

 ally on inner webs. Doivny 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 1.50-1.65, tarsus .90-1.00. Nest of dead 

 6 



