i-9 



Notes on the Mammals of Long Island, 

 New York. 



By Arthur H. Helme. 



(Revised to July 15, 1902.) 



The Mammalian fauna of Long Island is of especial inter- 

 est to students of the geographical distribution, individual 

 variation and development of local forms, the separation of 

 the island from the mainland preventing any influx of new 

 breeding stock from distant localities. The size of the island 

 is such that it is doubtful if new local forms would develop 

 except through a long period of interbreeding of individuals 

 from the same parent stock. The chances of this are largely 

 reduced as the field of the, species' wanderings is increased 

 .and vice versa. This is well illustrated in the case of the 

 Common Meadow Mouse and that of the Gull Island Mouse, 

 the latter being a local form of which the Common Meadow 

 Mouse was doubtless the parent stock. Long Island lying 

 as it does at about the border line between the Upper 

 Austral or Carolinian Fauna and that of the Transitional or 

 Alleghanian, presents in certain mammals forms that are 

 intermediate between those of the southern Atlantic coast 

 and those of the northeastern sections. Here certain birds 

 of the Alleghanian Fauna find the southern limit of their 

 breeding range on the coast, for instance the Black-throated 

 Green Warbler (Dendroica virens) and the Saw-whet Owl 

 (Nyctala acadica) both of which have been found breeding 

 on Long Island. Here, too, the Acadian Flycatcher (Empi- 

 donax virescens), Carolina Wren (Tliryoihorus ludovicianus) 

 and other Carolinian species find their northern breeding 

 limit on the coast. 



