The Audubon Societies 



125 



there are no such arbitrary divisions made by man. Birds know only the 

 dividing lines set by Nature's own hand — lines of temperature, of altitude, 

 of humidity or aridity, which mark out areas suitable for the existence of 

 species of certain habits and vigor. Man, indeed, has some power to interfere 

 with Nature's bounds, for he can, at will, drain marshes, cut down forests, 

 burn over vast tracts, or plant extensive fields with grains, crops, or orchards 

 of fruit. He can even bring water into the desert and change the very face 

 of Nature; and so, as we study the birds' map of America, we must all the 

 time keep in mind what man is doing. 



Let us now make a third outline, to help us remember what the map of the 

 birds is like, and then try to answer a few questions as to what man is doing 

 in his conquest of nature. 



Outline of Faunal Areas of Distribution in North America, according to 

 Dr. J. A. Allen and Dr. C. Hart Merriam 



Realm Region Sub-region Province Sub-province District Fauna 



. . ( Barren ground 



Arctlc t Alaskan-Arctic 



Isotherm of 32°. Tree-limit 



(Hudsonian 

 Canadian 

 Aleutian 

 Sitkan 



North Temperate 1 



North 

 American 



Warm 



Temperate 



w ■ , j Appalachian f Alleghanian 



Humld Austro-riparian 1 Carolinian 



(.Louisiaman 



VArid 



, ( Great plains I 



J Upper Sonoranx Great basin ( 

 } { Pacific coast 



Faunas not yet 

 worked out 



Euro-asiatic 



Isotherm of 70 



Central ) 

 American J ' 



Lower Sonoran 



American 



Tropical 



f Tamaulipan 

 \ St. Lucas 



Antillean Floridian 



i. Notice that there is little variation throughout the arctic realm, either in climate 

 or topography, and that the majority of forms found there are circumpolar in distribution . 



2. Notice that the cold temperate subregion is also an east to west division, being 

 made up of transcontinental coniferous forests, except on the Pacific coast. Compare 

 the temperature of Newfoundland with that of Lake Superior, Athabasca and Alaska. 



3. Notice that the warm temperate subregion is more greatly diversified than the 

 cold temperate. 



4. Notice that the humid and arid provinces which make up the warm temperate 

 subregion, form a north to south division along the 100th meridian, the dividing factor 

 being the amount of annual rainfall. 



5. Notice that the lower Sonoran subprovince comprises mostly open plains and 

 deserts in the western United States. 



6. Notice that there are two main highways from the American tropical realm into the 

 North American and arctic regions. These are through Central America and The Antilles. 



7. See Exercises, V, VI, VII, Bird-Lore. 



