No. 4.] DECREASE OF BIRDS. 477 



adapted itself to changing conditions, and has come out 

 of the woods and into the villages more than formerly. 

 Whether the advent and increase of the Colorado potato 

 beetle, on which it feeds, has had anything to do with this, 

 is, perhaps, worth investigating. 



Some observers report an increase of the scarlet tanager, 

 but others report a decrease, and the account nearly balances. 

 My own impression is that this bird was not so common 

 thirty years ago as now, but it fluctuates in numbers from 

 year to year. A few species beside the rose-breasted gros- 

 beak evidently are increasing. Forty-four observers report 

 the robin as increasing; four, no change; and seven, de- 

 creasing. A similar though less marked increase is reported 

 of the bluebird and song sparrow. 



The Causes of the Decrease of Birds. 

 In considering the causes of bird destruction, as men- 

 tioned in these reports and letters, it becomes evident that 

 man and his works are of the most importance. Beside 

 man all other destructive forces dwindle into insignificance. 

 The destruction of lairds by the elements or by their natural 

 enemies is not to be compared for a moment with that in- 

 flicted by man on all species that come within the scope of 

 his wants. Man's persecution is annual and perennial. It 

 gives a species no chance to recover. It seldom stops short 

 of extermination, unless restrained by stringent laws efii- 

 ciently enforced. 



Man the Exlerminator. 



The reports on the diminution of bird-life, as caused 

 directly or indirectly bj' man, may be tabulated as follows 

 to shoAV the relative importance of each cause : — 



