THE BLUEBIRD 265 



The Common Bluebird. 1 — The United States is a coun- 

 try of such vast extent, it is a physical mosaic of different 

 elevations, soils and climates. Roughly speaking, these are 

 its physical divisions: 



1. The eastern half, of ideal rainfall, bountiful harvests 

 and abundant shade. 



2. The Great Plains, fine for grazing, but mostly too dry 

 for agriculture. 



3. The Rocky Mountain region, embracing a perfect med- 

 ley of physical conditions, mostly high, rugged and rather 

 lacking in insect life. 



4. The arid regions of the country between the Rockies 

 and Sierra Nevadas, extending from southern Washington 

 to the City of Mexico, and including southern California. 



5. The region of great rainfall, on the northwestern Pacific 

 coast (northern California, Oregon and Washington). 



It is not strange, therefore, that we find typical species of 

 eastern animals developing westward into different colors, 

 and also different pelage, and designated scientifically by 

 different names. Take these examples by way of illustra- 

 tion: 



In the East we have the Common Bluebird. 



In the Rockies we have the Chestnut-Backed Bluebird, and 

 also the Mountain Bluebird. 



In Arizona we have the Azure Bluebird. 



In the Pacific states we have the Western Bluebird. 



And in Lower California the San Pedro Bluebird. 



Is it at all necessary that the general reader should know 



1 Si-a'li-a si-a'lis. Length, 6.75 inches. 



