The Audubon Societies 365 



northwestern Pacific coast, the Sitkan and the Aleutian, the names of which 

 suggest their location. These relatively small areas differ from the larger 

 ones chiefly in minor conditions. The matter of humidity in the Sitkan area, 

 due to frequent storms and dense fogs along the coast, renders the climate 

 heavy, moist and sunless much of the time, exactly the reverse of what we 

 shall find farther south in arid places. By reason of this abnormal amount of 

 moisture, the plumage of the birds found there is much darker than in adjoin- 

 ing faunal areas, where it is drier and the sun shines more. 



Roughly speaking, the warm temperate subregion includes the Mexi- 

 can tableland and all of the United States, except first, the cold temperate 

 heights of the great mountain-ranges, and second, the tip of Florida, a narrow 

 strip of coast-line along southern Texas, an even narrower strip along the 

 eastern coast of the Gulf of California and the extreme end of Lower Cali- 

 fornia, which belong to the American tropical realm. 



The first thing which strikes the eye, in looking at a faunal map of North 

 America, is the diversity of this warm temperate belt. Along the one hun- 

 dredth meridian, a little to the west of the Mississippi River, may be placed 

 an imaginary line, to indicate that at about this point there is a decided dif- 

 ference in the amount of the annual rainfall, from east to west. East of this 

 fine we speak of humid conditions; and, west of it, of arid conditions. By 

 measuring the number of inches of rain falling in any locality during a year, 

 one may get an idea of the degree of its humidity or aridity. It is easy to see 

 why certain crops cannot be successfully grown in the East, which flourish in 

 the West, and why arid lands must be irrigated before anything but desert 

 vegetation will thrive on them. 



Here, in our own country, we have one of the most interesting and impor- 

 tant problems of modern civilization to work out, learning what cereals, fruits 

 and crops may be grown in different places. Not only are all kinds of plants 

 affected by climatic changes, but also, to a less degree, birds and other animals. 

 We must, therefore, distinguish between the East and the West, the gulf and 

 ocean coasts, the great plains, plateaus, and desert and wooded areas of this 

 highly diversified warm temperate subregion. 



Just south of the Canadian fauna occurs a transition zone, which is broader 

 and more connected in the eastern than in the western United States. It is 

 called the Alleghanian fauna, and extends from inland Nova Scotia, over 

 most of New England, New York, Pennsylvania, and along the Appalachian 

 mountain system as far south as Georgia and Alabama, on westward through 

 southern Ontario and Michigan, all of Wisconsin, central a,nd southern Min- 

 nesota, over the northern two-thirds of the Dakotas, northern and eastern 

 Montana, Wyoming, and part of Nebraska, up into Assiniboia, Manitoba 

 and the edge of Alberta, taking in the Saskatchewan plains district, and 

 farther west appearing in broken islands throughout the great mountain 

 ranges as far south as Mexico. The eastern part of this transition belt is 



