ON TREES AND BIRDS. 



153 



amount of weed seed annually destroyed by these 

 birds in Iowa. Upon the basis of one-fourth of an 

 ounce of seed eaten daily by each bird, and supposing 

 that the birds average ten to each square mile, and that 

 they remain in their winter range two hundred days, we 

 shall have a total of 1,750,000 pounds, or 875 tons, of 

 weed seed consumed in a single season by this one 

 species. 



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FIELD SPARROW. 



