610 BULLETIN 50, UXITED STATES XATIOXAL 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 

 buflF, 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. —Wmg, 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 feiimle.—W\i\g, 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 Cahfornia (coast near Carmen 



o In general appearance the downy young of Larus occidentalis is not very unlike 

 that of Chroicocephalus atridlla, but the pattern of the head markings is very different. 

 & Six specimens. 

 c Ten specimens. 



