STERNA. 43 
color and less heavily blotched than those of 8S. 
Jorsteri. Hab. Hastern temperate North Amer- 
ica, and various parts of eastern hemisphere. 
70. S. hirundo Linn. Common Tern. 
i*, Tarsus not more than .65 (usually much less). 
Summer adult: Lower parts deep lavender-gray, 
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 bind 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. Downy 
young: Similar to that of S. hirundo, but 
usually darker 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 claw, .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. Hab. Circum- 
polar regions, south, in winter, to Middle 
States and California; on Atlantic coast 
breeding south to Massachusetts. 
71. S. paradiseea Briwn. Arctic Tera. 
f*?. Both webs of outer tail-feathers entirely white. 
Summer adult: Above delicate pale pearl-gray, 
fading into silvery white on upper tail-coverts 
