IV 



DISTRIBUTION 



The fact that birds are not universally distributed is known 

 to every one interested in natural history ; that the Mock- 

 ingbird is a southern, and not a northern bird is generally 

 understood. The exact limits of the breeding area of any one 

 bird are hardly to be defined even in New England, but the 

 region where it breeds commonly may now be definitely 

 mapped. 



Two important factors must be borne in mind in studying 

 the breeding areas of the birds of New England and New 

 York: the latitude and the altitude. If we pass from New 

 York city through southwestern Connecticut to New Haven, 

 then up the Connecticut Valley to northern Vermont, we note 

 in southern Connecticut the tulip-tree and the sweet gum ; 

 in central Connecticut we see them no longer, but we still 

 see oaks and hickories ; but by the time we reach Wells 

 Kiver in central Vermont, these too are left behind, and 

 patches of spruce and fir appear on the distant hillsides. 

 We have climbed only 407 feet from the sea, but we have 

 traversed nearly three degrees of latitude, and hence these 

 changes. They are due to a colder and moister climate at a 

 higher latitude. Had we left the train in the Connecticut 

 River Valley, at Greenfield, traveled westward to North 

 Adams, and then climbed Mt. Greylock, almost 3000 

 feet above the railroad, we should have noted the same 

 changes as we ascended the mountain ; the oaks and nut 

 trees would have disappeared, and been replaced by spruce and 

 fir. But here the changes would have been due to altitude. 



