1906.] BIRDS ABOUT OUR FARM HOMES. 187 



injure fruit crops to the amount of twenty million dollars. His 

 statement, based on the value of farm products as given in the 

 Reports of the Bureau of Statistics of the United .States 

 Department of Agriculture for 1904, gives the loss from insect 

 depredations for that year as seven hundred and ninety-five 

 million one hundred thousand dollars, and this is believed to be 

 a conservative estimate of the tax now imposed by injurious 

 insects on the people of the United States, without reckoning 

 the millions of dollars that are expended annually in labor and 

 insecticides in prosecuting the fight against insects.* 



In considering the losses caused by insect pests, and the 

 possibility of preventing them, it is well for us first to observe 

 how nature, if left to herself, provides a system of checks, which 

 in the forest or wilderness operate to maintain the balance of 

 life so nicely that, ordinarily, neither low-growing plants, 

 shrubbery, nor trees, suffer greatly from the attacks of insects. 



First, birds, bats, other insectivorous mammals, batrachians, 

 reptiles, and predaceous insects, feed upon injurious insects, 

 and thus hold their increase in check. These are the primiary 

 controlling agencies. When these fail, parasitic insects, 

 increasing, attack the insect hosts, and when these also prove 

 ineffective — when vegetation is destroyed and the food supply 

 •exhausted — disease and starvation kill off the swarming in- 

 sects and give vegetation a chance to renew itself. These latter 

 agencies, which are so effective under natural conditions, are 

 of less immediate service to the farmer, however, in checking 

 injurious insects than are the birds, for, although parasites, 

 disease or starvation, ultimately check many great outbreaks of 

 injurious insects, these most effective checks do not avail until 

 such insects are most numerous, usually in the second year 

 of their abundance, when it is too late to save the crops. The 

 birds, on the contrary, form a mobile standing army, that can 

 Tje concentrated at once upon any insect outbreak, reducing it 

 before it has done much harm. This quelling of insect inva- 

 sions by birds is a common occurrence, but is seldom noticed 

 for the reason that birds often suppress the insect uprising 

 before it has become apparent to common observation, or has 

 done any considerable injury. The instances where birds fail 

 to check insect outbreaks at once attract attention, for then 



* "The annual loss occasioned by destructive insects in the United States," by C. 

 i. Marlatt, Year book, U.-S. Department of Agriculture, 1904, p. 464. 



