^ 5 



\ 



course, be sharply drawn. The change from one to another is 

 gradual, and thus between the two a neutral strip exists in which 

 will be found species characteristic of each. Just such a condition 

 is found in this vicinity; the northern boundary of the Carolinian 

 Fauna over-lapping the southern boundary of the Alleghanian 

 Fauna in the valleys of the Delaware, Hudson, and Connecticut. 

 In other words, we have here on the one hand a number of birds 

 which are found no farther north, and on the other certain species 

 which are found no farther south. That is, in the breeding 

 season; for among birds only the nesting ranges are of value in 

 determining the boundaries of faunas. 



The southern limit of the Carolinian Fauna on the Atlantic 

 Coast is near Norfolk, Virginia; its northern limit, on the coast, as 

 said above, is in the vicinity of New York City. To be more exact, 

 a careful study of the nesting ranges of certain species shows that 

 the most northern points at which they are regularly found is Port 

 Jervis in the Delaware Valley, Fishkill in the Hudson River Valley, 

 and Portland in the Connecticut River Valley. These localities 

 then may be considered as defining the northern limits of the 

 Carolinian Fauna in the valleys in which they are placed. In the 

 more elevated country between these points it is doubtful if the 

 limits of the fauna reach quite as far north, for river valleys, both 

 because they offer a natural pathway for the extension of a bird's 

 range, and because of the higher temperature prevailing in them, 

 tend to carry northward the boundaries of faunas. Eastward, 

 along the Connecticut shore, the Carolinian Fauna may reach the 

 mouth of the Thames. Long Island, although farther south, 

 belongs for the most part in the Alleghanian rather than the 

 Carolinian Fauna. Numbers of species common and even abund- 

 ant in the Lower Hudson Valley are exceedingly rare on Long 

 Island, especially on the southern shore. But along the northern 

 shore, or older part of the island, where deciduous trees abound, 

 there is an evident trace of the Carolinian Fauna shown by the 

 regular occurrence of the Blue-winged Warbler and Acadian 

 Flycatcher. 



The following Carolinian birds are found every summer within 

 50 miles of New York City, and all but two or three are known to 

 nest regularly here. Their occurrence northward beyond these 

 limits is rare and irregular, and but two or three have been known 

 to nest north of the 50 mile line. 



