122 



BIRDS OF THE COMMANDER ISLANDS. 



tip is rather large. In No. 106625 the white mirror is much larger than 

 in the quill figured, crossing both webs in one wing, and nearly con- 

 fluent with the gray wedge. Two specimens of L. affinis are without a 

 trace of the white mirror, while only the one figured has a small white 

 spot ; the absence of a white mirror seems to be the rule iu this species, 

 " and only to be found in very old birds (not one of thirteen breediug- 

 birds obtained on the Petchora had it"), according to Saunders (P. Z. S., 

 1878, p. 172). 



In the third and fourth primaries of L. schistisagus I find in all speci- 

 mens a somewhat unique character, inasmuch as the gray wedge on 

 the inner web terminates in a large white mirror, as shown in the fig- 

 ure.* In L. apnis there is, at most, a narrow white line separating the 

 gray from the black. This strongly marked character of L. schistisagus 

 is not due to an extremely old age of the specimens here in question, for 

 it is found even in the young bird. No. 101660 is still gray on head and 

 belly ; the new slate-colored feathers have nearly all appeared on the 

 back, but the wing-coverts are still mostly brownish gray, the tail- 

 feathers are blackish towards the end, white at base, mottled with 

 brownish-gray, and the bill is dusky, becoming lighter on the basal 

 half of the tomia. The primaries (the first two not yet fully out) are 

 pale brownish-gray, the outer webs and tips much darker dusky ; iu 

 the first one there is a large white mirror on the inner web about 20™°^ 

 from the tip ; the second one is without any definite pattern, but the 

 third has a gray wedge terminated with white, as in the old bird, but 

 more restricted, while on the fourth primary the pattern is stronger de- 

 fined and the extent nearly exactly as in the third primary of the adult 

 birds. 



The above comparison should be sufiScient to reitiove all doubts as to 

 the specific validity of Larus schistisagus, and will, in connection with 

 what is said in "Orn. Expl. Kamtsch." under this species, enable the 

 student of Eastern Asiatic birds to distinguish the different species of 

 the very difiQcult group of Herring-gulls. 



I.-LARUS SCHISTISAGUS: 



♦This feature is not well represented in the previous figure (Orn. Expl, Kamtsch., p. 70, fig. 4, cf. 

 tfootuote, p. 362), and a new one is therefore given here (pi. viii). 

 tWing molting. 



