52 



army of resident birds were shortly added multitudes of wander- 

 ing ones from distant regions. In the autumn the earth so 

 teemed with mice that one could scarcely walk without treading 

 on them; but so rapidly were they devoured by the trained 

 army of their enemies that in spring it was hard to find a single 

 survivor, even in the barns and houses. The storks all left in 

 winter, and by August, 1873, even the short-eared owls had 

 vanished. Mice were now so scarce that the little resident 

 burrowing owls were almost famished, and hung about the 

 houses of the settlers to pick up scraps of garbage that were 

 thrown to them. 1 



In many parts of the western United States the destruction 

 of the natural enemies of rodents has now gone so far that these 

 animals have increased greatly in numbers. Whole communities 

 find themselves compelled to turn out to hunt "jack rabbits." 

 The Biological Survey has been obliged to organize the farmers 

 over large areas in the work of poisoning mice, gophers and 

 ground squirrels. Bounties have been offered on the heads of 

 these creatures, and large sums have been paid out for their 

 destruction. In one case in Montana in 1887 a special session 

 of the Legislature was called to repeal the bounty act and save 

 the State from bankruptcy. In the Humboldt valley in Ne- 

 vada, in 1907-08, the loss to crops by an irruption of field 

 mice was estimated conservatively at $250,000. 2 It was esti- 

 mated that 2,000 raptorial birds and 1,000 predatory mammals 

 gathered and assisted to quell this outbreak, and that they de- 

 stroyed 1,350,000 mice each month, yet there were not enough 

 of these carnivorous creatures left in that country to check the 

 pest materially, and the farmers were compelled to resort to 

 poisons. 2 



In New England our common hares, miscalled rabbits, are 

 kept in check by the hunter. But field mice, not subject to this 

 check, destroyed thousands of young fruit trees during the 

 winters of 1903-04 and 1904-05. 



Hudson, W. H.: The Naturalist in La Plata, 1895, pp. 58-63. 



2 Piper, Stanley E.: Mouse Plagues and their Control and Prevention, Yearbook, United 

 States Department of Agriculture, 1908, pp. 302, 304. 



