THE BLUEBIRD 265 
Tue Common Briuesirp.'—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. 
