610 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
LARUS OCCIDENTALIS Audubon. 
WESTERN GULL. 
Adults in summer (sexes alike).—Head, neck, rump, upper tail- 
coverts, tail, and entire under parts, including axillars and under 
wing-coverts, immaculate pure white; back, scapulars, and wings 
uniform neutral gray to deep neutral gray, the secondaries, tertials, 
and proximal primaries broadly (for 25 mm. or more) tipped with 
white; four outer primaries with outer webs black, becoming more 
grayish basally (especially the fourth), the outermost one with its 
terminal portion, for about 50 mm., abruptly white, crossed, on one 
or both webs, by a subterminal black bar; second to fifth primaries 
(from outside) tipped with white, the fifth with much more of neutral 
gray than black on outer web; sixth primary with the black reduced 
to a subterminal bar; bill deep yellow, the mandible with a sub- 
terminal lateral spot of red; iris brown; bare orbital ring vermilion 
red; legs and feet yellow (in life). 
Adults in winter.—Similar to summer adults, but pileum and hind- 
neck streaked with dusky. 
Young.—Upper parts grayish brown or: deep brownish gray, 
irregularly spotted or marbled with grayish white, the remiges, 
primary coverts, and rectrices uniform dull black or dark grayish 
brown, narrowly tipped with white; under parts grayish brown or 
brownish gray, nearly uniform on breast and abdomen, elsewhere 
more or less clouded or irregularly spotted with grayish white; 
bill blackish terminally, flesh color or pale brownish basally; iris 
brown; legs and feet flesh color (pale brownish in dried skins). 
Downy young.—General color pale dull vinaceous-buff or brownish 
buff, slightly more grayish on back, rump, flanks, etc.; head with 
numerous large, well-defined but irregular black spots, of which the 
largest is on the occiput, or on median portion of forehead, at base 
of culmen, one on middle of crown, and one near base of mandible; 
forearm, back, and rump with large, distinct, and for the most part 
sharply defined, irregular black spots or marblings.* 
Adult male.—Wing, 397-447. (423.7) ; tail, 150-177 (164.1) ; exposed 
culmen, 52-59 (57); tarsus, 63-68 (65.9); middle toe, 60.5-65.5 
(62.2).° 
Adult female.—Wing, 368-433 (400.6); tail, 146.5-167.5 (156.9); 
exposed culmen, 51-58 (53.8); tarsus, 58-66 (61); middle toe, 55.5-63 
(58.6).° * 
Pacific coast of North America, from western Mexico to British 
Columbia; breeding from Lower California (coast near Carmen 
@ In general appearance the downy young of Larus occidentalis is not very unlike 
that of Chroicocephalus atricilla, but the pattern of the head markings is very different. 
b Six specimens. 
« Ten specimens. 
