STERXA. 43 



color and less heavily blotched than those of S. 

 forsteri. Hab. Eastern temperate North Amer- 

 ica, and various parts of eastern hemisphere. 

 70. S. hirundo Linn. Common Tern. 

 /(^ Tarsus not more than .05 (usually much less). 

 Summer adult : Lower parts deep lavender f,'ra3', 

 changing to -white only on lower tail-coverts 

 and on sides of head adjacent to the black 

 cap ; upper parts deep pearl-gray, the tips of 

 secondaries, rump, upper tail-coverts, and tail 

 pure white, in marked contrast; bill rich car- 

 mine, usually without distinct blackish tip ; 

 feet intense carmine. Winter adult : Similar, 

 but lower parts white (sometimes tinged with 

 grayish), and forehead, crown, and fore part 

 of lores white, the crown streaked or mixed 

 with black. Young: Orbital region, occiput, 

 and hind part of crown dull black; forehead, 

 anterior part of lores, and crown white, the 

 latter stained with brown and mixed with 

 blackish ; feathers of dorsal region and wings 

 tipped with pale buff and marked with a sub- 

 terminal crescent or lunule of brownish dusky, 

 these markings larger on tertials and longer 

 scapulars, and smaller on back ; lower rump, 

 upper tail-coverts, and entire lower parts, 

 white, the chin, throat, and sides of jugulum 

 and breast, stained with pale dull brownish ; 

 basal half of bill dull orange-red, terminal 

 portion blackish ; feet light reddish. Doicny 

 young: Similar to that of S. hirundo, but 

 usually dai-ker colored. Length 14.00-17.00, 

 wing 10.00-10.75, tail 6.50-8.50 (forked for 

 4.00-5.00), culmen 1.08-1.40, depth of bill 

 through base 30, tarsus .55-.65, middle toe, 

 with daw, .80-.85. Eggs 1.62 X 1-15, not 

 distinguishable with certainty from those of 

 S. hirundo, but usually with darker ground- 

 color and heavier spotting. Hah. Circum- 

 polar regions, south, in winter, to Middle 

 States and California; on Atlantic coast 

 breeding south to Massachusetts. 



71. S. paradissca BrI'nn. Arctic Tern. 

 /'. Both webs of outer tail-tVatliers entirely white. 



Summer adult: Above delicate pale pearl-gray, 

 fading into silvery white on upper tail-covcrts 



