BIRDS OF NEW YORK 



31 



tribution of plants and animals, which properly determines the boundaries 

 of the life zones, agrees so nearly with the limits determined by these laws 

 of temperature control that the boundaries shown on the maps of the 

 Biological Survey have been fixed according to the temperature. This, 

 while accurate in general, is slightly misleading when applied to the dis- 

 tribution of birds and mammals in New York State, on account of the 

 peculiar conditions obtaining. 



New York is so situated topographically that it neither connects inti- 

 mately with the Boreal zone on the north nor with the Upper Austral on 

 the south. The Adirondacks are separated from the main Canadian zone 

 by lowlands of less than 500 feet elevation which are typicallv Alleghanian 

 in fauna. The coastal region, Staten Island, Long Island, and the Lower 

 Hudson valley, is practically or nearly shut off from the southern coastal 

 plain by the encroachment of the New Jersey highlands and by the tidal 

 waters, which though not wholly efficient as barriers, nevertheless check 

 to an appreciable extent the influx of the usually sedentary species or less 

 ambitious migrants of the Carolinian fauna. The Hudson vallev, extend- 

 ing northward between two highlands of Boreal affinities, is still further 

 cut off from easy connection with the Carolinian area by the extension of 

 the Hudson highlands diagonally across the valley. The lowland of western 

 New York is practically shut off from direct communication to the south- 

 vvartl with the Carolinian area by the broad northern expansion of the 

 Alleghany plateau which extends westward from the Catskills entirelv 

 across the southern j^ortion of the State bordering on Pennsvlvania. Thus 

 the only efficient connection of this lowland with the Upper Austral is by 

 a narrow strip along Lake Erie, and through southern Ontario and Michigan. 

 For this reason the Carolinian birds which breed in the Lake Ontario low- 

 land of New York are almost entirely migratory species like the Chat and 

 Large-billed water-thrush, the more sedentary or resident species failing 

 to establish themselves permanently on account of the severe winters 

 with deep snows, which destroy such species as the Bobwhite and Carolina 



