36 THE IMPOETANCE OF BIKD LIFE 



hours was 46,000, or slightly more than one seed 

 to the square foot. Therefore, the grand total 

 of weeds eliminated in a year from any one farm 

 must be very great. 



Effect on Rodents 



We now reach the third province of birds in the 

 cause of agriculture. This is their destruction 

 of injurious rodents. 



It is not commonly realized what a wide- spread 

 menace these little animals are. Collectively 

 they make an enormous group, comprised of 

 squirrels, gophers, lemmings, wood-mice, field- 

 mice, rats, and many others. Their chief food 

 is roots or green crops, and they are ultra-prolific. 

 All people are familiar with the procreant multi- 

 plication of the common house-mouse, and field 

 rodents are fully as productive. 



Their prolificness at times is amazing. During 

 ordinary seasons they merely seem to hold <their 

 own in numbers against natural enemies birds, 

 cats, and small vermin. Even in these days of 

 " peace " their reproduction is great, but not 

 sufficient to attract their enemies in greater force. 

 The presence of fifty or a hundred field-mice on 

 an acre of alfalfa does not affect the crop, and 

 makes merely fair hunting for vermin. Pres- 



