BIRDS OF NORTH AND MIDDLE AMERICA, 687 
not greater than its width at same point. Wing long and pointed, 
the outermost primary decidedly longest and exceeding distal sec- 
ondaries by more than half the length of wing; primaries tapering 
terminally, pointed at tips. ‘Tail less than half as long as wing 
(except middle pair of rectrices), nearly truncate, the rectrices with 
broadly rounded ends but with extreme tips submucronate; middle 
pair of rectrices elongated (sometimes greatly so), tapering to their 
acuminate tips, their plane horizontal throughout. Tarsus as long 
as or longer than middle toe with claw, rather slender, the acrotarsium 
with a single row of transverse scutella, except extreme upper por- 
tion, the planta tarsi with small, roughened or spiculate scales, the 
sides of tarsus with larger, less prominent scales; outer toe nearly 
as long as middle toe, the inner toe decidedly shorter; hallux very 
short; claws moderately large, rather strongly curved and acute; 
anterior toes fully webbed, the anterior margin of the webs not at 
all incised. 
Coloration.—Adults with upper and anterior portions of head 
dusky, the rest of head, and neck, straw yellowish; upper parts 
plain grayish brown or brownish gray, darker on primaries and tail; 
under parts white anteriorly, shading into brownish gray posteriorly. 
Young more or less barred. (One species with a dusky phase, 
immaculate in adults, barred with rusty or cinnamomeous in young.) 
Range.—Circumpolar regions, soutnward in winter as far as Persian 
Gulf, Cape of Good Hope, Australia, Galapagos Archipelago, southern 
Briail, etc. (Two species.) 
° 
KEY TO THE SPECIES OF STERCORARIUS, 
a. Length of supra-nasal saddle decidedly greater than distance from its anterior 
end to tip of maxillary unguis; middle pair of rectrices 164-235 mm. long; tarsi 
black, like feet. (Circumpolar regions, southward in winter as far as Brazil, 
Cape of Good Hope, Australia, Galapagos Archieplago, etc.) 
Stercorarius parasiticus (p. 687). 
aa, Length of supra-nasal saddle not greater than distance from its anterior end to 
tip of maxillary unguis; elongated middle pair of rectrices 238-368 mm, long; 
tarsi light-colored (bluish in life), in contrast with black of feet. (Circumpolar 
regions, southward in winter to Gibraltar, Japan, New England coast, etc., 
casually to California, Florida, etc.).......... Stercorarius longicaudus (p. 694). 
STERCORARIUS PARASITICUS (Linnzus.) 
PARASITIC JAEGER. 
Adults, light-colored phase (sexes alike).—Pileum and loral region 
grayish brown; rest of head, together with neck and under parts 
except under tail-coverts, immaculate white, the head more or less 
strongly tinged with straw yellow; upper parts uniform brownish 
gray, becoming darker or dusky on primaries and tail; anal region 
and under tail-coverts uniform brownish gray; bill light horn color, 
