BIRDS OF NORTH AND IMIDDLE AMERICA. 



613 



Downy young. — Dull buffy grayish white, the under parts (except 

 throat) immaculate; head marked with irregular spots of black, 

 irregularly distributed; back, wings, and rump clouded with dusky 

 grayish; bill black, tipped with yellowish; legs and feet brownish (in 

 dried skins). 



Adult male.—Wiwg, 401-419 (410); tail, 162.5-168 (165.2); ex- 

 posed culmen, 52.5-56 (54.2); tarsus, 60-62 (61); middle toe, 

 57.5-59.5 (58.5).« 



Adult female.— Wmg, 401-417 (407.5); tail, 159-166 (161.4); ex- 

 posed culmen, 45.5-51.5 (48.4); tarsus, 54-59 (56); middle toe, 

 49-53 (51. 2). ^ 



« Two specimens. 



^ Five specimens. 



In view of the paucity of material examined, I follow the decision of the A. O. U. 

 Committee in uniting the North Ameiican and European birds of this species. Never- 

 theless, the differences in size and coloration in the series examined are so marked that 

 [ cannot help believing thaf careful and unbiased examination of adequate material 

 will phow that they are separable as subspecies. The series examined by me plainly 

 shows the following difference between the North American and European birds (see 

 "Key" on p. 582): — 



k. Smaller (wing 401-419, averaging 410 in male, 405.5 in female; culmen 45.5-56, 

 averaging 54.2 in male, 48.6 in female; tarsus 54-62, averaging 61 in male, 56 in 

 female ; outermost primary with terminal white area usually without interruption 

 by a subterminal black bar, the latter if present very small and rarely continu- 

 ous. (Northern Em'ope, southward in \vinter to Mediterranean , Black, and Caspian 



seas; occasional in northeastern North America.) Larus argentatus argentatus. 



kk. Larger (wing 417-465, averaging 452 in male, 424.2 in female; culmen 48-63. 

 averaging 60 in male, 53.8 in female; tarsus 58-68, averaging 66.1 in male, 60.5 

 in female; outermost primary with white on terminal portion usually di\dded 

 into two separate areas by a subterminal spot or bar of black, this rarely less 

 than 12.5 mm. wide, often extending to extreme tip, then reducing the white to 

 a subterminal spot. (Northern North America, southward in T\dnter to Bahamas, 

 Cuba, Yucatan, western Mexico, etc.) Larus argentatus smithsonianus. 



The European birds are probably divisible into two forms. 



