Light-bellied Brent 159 



Geographical Distribution 



In addition to Russia, the light-bellied brent occurs in Eastern Arctic America from 

 Parry Island to Greenland inclusive, and from 73 N. Lat. northwards "as far as land is 

 found." It is also met with as a winter straggler in the Mississippi valley. In Europe it 

 has been found locally, wintering with the typical form, but in far less numbers. In Russia 

 it was found by Middendorff, who also did not recognise it, on the western part of the 

 Taimyr peninsula, by Mr. Trevor-Battye in Kolguev, and by Messrs. Fielden and Brown in 

 Novaia Zemlia, the specimen from the latter locality being distinguished by the white spots 

 becoming confluent on the anterior surface of the neck. 



I have only seen one example of this bird of Russian origin, which was brought by 

 Middendorff from the Taimyr peninsula, and I am able to state that it agrees in colouring 

 with the drawing on Plate 17. We may thus consider with certainty that the Kolguev and 

 Novaia Zemlia birds do not essentially differ from the one figured, although the latter was 

 obtained in April 1889 on the island of Monomoi, in the State of Massachusetts. I cannot, 

 however, decide whether there are any differences between the European and the American 

 B. bernicla glaitcogaster, since I have not had a single example of the latter in my hands. 

 It would be no less important to examine the intermediate forms between the light-belly and 

 the brent which Mr. Trevor-Battye writes of in his book on Kolguev, but it seems that this 

 author did not bring back any specimens. My hopes of receiving Kolguev examples from 

 Mr. Buturlin, who made a scientific expedition to that island in 1902, have also not been 

 realised, as that talented and energetic naturalist arrived on Kolguev after the geese had 

 finished moulting, and was then too late for the great catch of moulting birds by the 

 Samoyeds ; such fledged brent as he shot proved to be of the typical form. 



The simultaneous occurrence on Kolguev of the typical and the light-bellied forms, 

 that is, of two distinct races of one species, is at first sight a very unusual circumstance, 

 but analogous instances are known among insects. Apparently we may have either 

 (1) dimorphous forms of one species, or (2) two separate independent species, breeding 

 together and producing as the result of crossing those intergrading examples of which Mr. 

 Trevor-Battye speaks. The latter supposition is, however, in itself but little probable, since, 

 beyond the substitution of light for slate colouring on the under surface of the body, no 

 difference exists between these birds. 1 The first hypothesis, viz. that B. glancogaster is a 

 simple dimorphous form, as it seems to me, explains very simply the circumstance of these 

 geese being found breeding together. Among Lepidoptera I know cases where, for 

 example, a certain species is dimorphous in one locality (sometimes only with the males, 

 at others only with the females), while in other places the same species may appear in one 

 or other of its forms as a permanent variety or sub-species. 



Thus there is a species of butterfly of the genus Lycczna, in which in a certain 

 locality the males are dimorphous — some with brown wings, others with blue ; while all 

 the females are uniformly brown. In other localities this same species shows a mono- 

 morphous male, for example, with brown, and elsewhere with blue wings ; and this 

 phenomenon is permanent. 



The same is the case, I think, with this goose, which is dimorphous in Kolguev, 



1 Which still requires further investigation, at present impossible from the lack of material for comparison, with the exception of 

 the Taimyr skin of the light-bellied example. 



