Vol. XIX 

 190 



1 KoBBE, The Status of Certain Species of Larus. IQ 



THE STATUS OF CERTAIN SUPPOSED SPECIES OF 

 THE GENUS LARUS. 



BY WILLIAM H. KOBBE. 



The genus Lams is one of the five or six genera into which the 

 subfamily Larinai is divided. This subfamily, together with the 

 subfamily Sterninai (which we may almost call artificial divisions) 

 constitute the family Laridee, or the Gulls and Terns, of which the 

 Larinae are the Gulls and the Sterninae the Terns. This is by far 

 the largest of the three families constituting the order Longi- 

 pennes or long-winged swimmers. The genus Larus contains 

 about twenty-one American species, which show a great variability 

 in size and coloration of certain parts, so connected, however, by 

 intermediate forms that systematists are unable to base generic 

 distinctions upon these differences. So the many species still 

 comprise one genus, in which the specific value of the birds and 

 their complicated changes of plumage demand much further study. 



In speaking of Gulls it may be well to recall the words of Dr. 

 Coues : " Several circumstances conspire to render the study of 

 these birds difficult. With some exceptions, they are almost iden- 

 tical in form; while in size they show an unbroken series. Indi- 

 vidual variability in size is high ; northerly birds are usually 

 appreciably larger than those of the same species hatched further 

 south; the $ exceeds the ? a little (usually); very old birds are 

 likely to be larger, with especially stouter bill, than young or 

 middle-aged ones. There is, besides, a certain plasticity of 

 organization, or ready susceptibility to modifying influences, so 

 marked that the individuals hatched at a particular spot may be 

 appreciably different in some slight points from others reared but 

 a few miles away. One pattern of coloration runs through nearly 

 all the species; they are uiJiite, with a darker mantle {stragtihim), 

 and in most cases with black crossing the primaries near the end, 

 the tips of the quills white. The shade of the mantle is very 

 variable in the same species, according to climate, action of the 

 sun, friction, and other causes ; the pattern of the black on the 

 quills is still more so, since it is contiiuially changing with age, at 

 least until a final stage is reached. Incredible as it may appear, 



