BIRD ENEMIES INTRODUCED BY MAN 143 



maturity would give a total of 5,600,000 young 

 birds for the first brood. We may also estimate the 

 second brood from the data furnished by the cen- 

 sus, in accordance with which there would be in 

 Massachusetts about 



300,000 pairs of robins. 



250,000 pairs of English sparrows. 



78,000 pairs of house wrens. 



72^000 pairs of bluebirds. 



700,000 pairs in all. 



Assuming again two young reared in the second 

 brood gives a total of 1,400,000. This, added to 

 the number of the first brood and to the number of 

 adults, gives a total of 12,600,000 birds on the farms 

 of Massachusetts. In accordance with the previous 

 estimate that cats kill about one and a half millions, 

 this would mean that they destroy annually about 

 one eighth of the total bird population found on the 

 farms of Massachusetts. 



Mr. Forbush, in his bulletin on the " Domestic 

 Cat," quotes the following estimates: — 



Dr. George W. Field, chairman of the Massachusetts 

 Commission on Fisheries and Game, estimates that there 

 is at least one stray cat to every hundred acres in the 

 State, and that each cat kills on the average at least one 

 bird every ten days through the season, making the an- 

 nual destruction of birds by stray cats in the State 

 approximate 2,000,000. 



Dr. A. K. Fisher, in charge of Economic Investiga- 



