Climatic Variation in Color and Size of Song Sparrows 165 



but west of the Rocky Mountains, where there are widely varying climatic 

 conditions, sixteen subspecies of Song Sparrow are known, twelve of them 

 from California alone. 



There is a striking relation between the colors of the various races and 

 the aridity and the humidity of the areas they inhabit. Thus the palest- 

 colored race, the Desert Song Sparrow (No. 5, on the accompanying illus- 

 tration), Melospiza c'lnerea fallax inhabits the most arid portion of North 

 America, the desert region of Nevada, Arizona and southeastern California, 

 where the annual rainfall averages about six inches; while the darkest-col- 

 ored race, the Sooty Song Sparrow (No. 2, Melospiza cinerea rufina) , inhabits 

 the most humid portion of North America, the coast region of British 

 Columbia and southern Alaska, where the annual rainfall may reach one 

 hundred and twenty-five inches. 



Note that, in obedience to the law that animals increase in size toward 

 the north, the largest race, the Aleutian Song Sparrow (No. i, Melospiza 

 cinerea cinerea ), is the most northern, and, the smallest race, the Mexican 

 Song Sparrow ( No. 6, Melospiza cinerea mexicana) , is the most southern. 



Between the lightest and the darkest, the smallest and the largest Song 

 Sparrows, however, there is complete intergradation in accordance with the 

 change in the conditions which afifect their color and size. 



NIGHTHAWK ON NEST 

 From nature, by J. E. Seebold. Carlisle, Pa. 



