14 BIRDS OF THE NEW YORK CITY REGION 



Most of our breeding birds belong to the Alleghanian or 

 Transition Zone, and in the highest parts of northwestern 

 New Jersey there is a trace at least of the Canadian Zone. 



Twenty-five years ago the limits of these faunas in our 

 Region could be stated with a fair degree of definiteness on 

 existing information. Unfortunately, the much more detailed 

 knowledge of the exact distribution of our breeding birds at 

 the present time has tended to make these lines of demarca- 

 tion more obscure, so that many local students are beginning 

 to find life zones a difficulty rather than an aid in their work. 

 While it is true that the number of apparent exceptions has 

 greatly increased, the causes back of these exceptions are yet 

 to be determined. I know of no more interesting field for 

 local research. Again it is beyond dispute that the boundaries 

 of life zones correspond in a general way with lines of equal 

 temperature. But in so small an area as this, differences of 

 climate are scarcely perceivable. Let no one suppose that 

 there is any marked difference in climate between those parts 

 of our Region which may be regarded as Carolinian and those 

 which are Alleghanian. What is true is that any territory 

 which is definitely in any life zone lies in between two iso- 

 thermal lines (lines of equal temperature) . This Region being 

 largely neutral territory, as explained above, does not possess 

 a well-marked isothermal line dividing it into two parts. 

 The exigencies of space forbid further discussion here. The 

 situation is particularly complicated, as a local problem, 

 but this complication must not be construed as invalidating 

 the concept of life zones. 



I. The Carolinian or Upper Austral Zone. The fol- 

 lowing birds are generally regarded as Carolinian species, 

 and occur more or less regularly in our area. Their exact 

 status can be found in detail in the annotated list. While all 

 of them were formerly believed to reach their normal northern 

 limits as breeding birds in this Region, this is now known to 

 be the case only with those marked with an asterisk (*). 



