550 Capt. Sabine's Memoir on the Birch of Greenland, t^c. 



also rayed with black. The young birds when full grown have 

 this autumnal ajapearance with additional differences correctly 

 described in the Fauna Suecica ; the bill is black instead of yel- 

 low; at the back of the neck the feathers are tipt black, forming 

 a narrow crescent-shaped patch ; the wing coverts are tipt black, 

 forming a bar across the wings ; primary quills black, with more 

 or less of the inner webs in different specimens white : tail tipt for 

 half an inch with black, except the outer feather on each side, the 

 second having only a spot on the inner web. It is worthy of ob- 

 servation that the outer tail feathers are somewhat longer than the 

 inner ones, giving the tail an appearance of being slightly forked ; 

 this is more perceptible in the young birds than in the old ones. 



The specific name of tridactylus (though given by Linneus to 

 the immature bird) appears preferable, as being more appropriate 

 than that of Rissa : it is therefore adopted. I am inclined to 

 suppose that this species attains maturity at the age of one year. 

 In June none were seen Avith spotted plumage ; early in October 

 several immature birds were killed, being marked as above de- 

 scribed : the specimens noticed by Montagu as killed in the 

 month of March, and supposed by him to be in complete plu- 

 mage, had evidently not got rid of all the black markings on the 

 wing coverts, which I believe would have taken place, had they 

 lived a few weeks longer. 



The L. tridactylus of Gmelin and Miiller, and the Tarrock Gull 

 of the Arctic Zoology, are the young bird after it has lost the black 

 bar upon the wing, and before the colour has disappeared from 

 the neck and from the tips of the tail-feathers. It is apprehended 

 that the Larus cinerarias of Fabricius is the tridactylus in winter 

 plumage : its rarity in Greenland, as noticed by him, may be ac- 

 counted for by the probability that most of these Gulls migrate 

 southwards during that season. 



23. Larus 



