72 USEFUL BIRDS. 



destruction of these insects may have been due in part to 

 the hard winter that ensued, but the effect produced by the 

 birds was most obvious. 



Such instances of the quelling of insect outbreaks by birds 

 are noticeable, but the regulative influence steadily and 

 perennially exerted by them, which tends to keep hundreds 

 of species of injurious insects below the point where their 

 injury to trees and plants would become apparent, is very 

 seldom appreciated. 



THE INCREASE OF INJURIOUS INSECTS FOLLOWING 

 THE DESTRUCTION OF BIRDS. 



Many cases have been noted where the destruction of birds 

 has been followed by an immediate increase in the numbers 

 of injurious insects. Frederick the Great, king of Prussia, 

 being particularly fond of cherries, was annoyed to see that 

 the Sparrows were destroying his favorite fruit. An edict 

 was issued ordering Sparrow extermination. All the re- 

 sources of the fowler were brought to bear, and the cam- 

 paign was so successful that not only were the Sparrows 

 destroyed, but many other birds were either killed or driven 

 away by the extraordinary measures taken against the Spar- 

 rows. Within two years cherries and most other fruits were 

 wanting. The trees were defoliated by caterpillars and other 

 insects, and the great Frederick, seeing his error, imported 

 Sparrows at considerable expense to take the place of the 

 birds that had been killed. 1 



In the year 1798 the forests in Saxony and Brandenburg 

 were attacked by a general mortality. The greater part of 

 the trees, especially the firs and pines, died as if struck at 

 the roots by some secret malady. The foliage was not de- 

 voured by caterpillars ; the trees perished without showing 

 any signs of external disease. This calamity became so gen- 

 eral that the regency of Saxony sent naturalists and skillful 

 foresters to find out the cause. They soon found it in the 

 multiplication of one of the lepidopterous insects, which in 

 its larval state fed within the tree upon the wood. When- 



1 Agricultural Value of Birds, by E. A. Samuels. Annual Report of the Mas- 

 sachusetts State Board of Agriculture, 1865-66, pp. 116, 117. 



