BIRD ENEMIES INTRODUCED BY MAN 145 



cats kept by families living in the more crowded 

 portions of the large cities can do little harm to 

 native birds, because few birds are present. In 1910 

 there were east of the Mississippi River 37 cities 

 having a population of over one hundred thousand, 

 making a total of 10,700,000, comprising about 

 3,700,000 families. Subtracting this number from 

 the total number of families given above leaves 

 3,700,000 families living in towns and cities where 

 cats might find birds to kill. The number of fami- 

 lies living in the centers of cities with a population 

 of less than one hundred thousand, where few birds 

 are found, would be about balanced by the number 

 of families living in the suburbs of the large cities 

 where birds are found. 



At the last census there were about one million 

 families east of the Mississippi River living in in- 

 corporated places of less than twenty-five hundred. 

 This added to the previous number gives 4,700,000 

 families living in the towns and smaller cities where 

 birds are found quite commonly. 



Mr. Forbush's investigations in Massachusetts 

 showed that in the towns the average number of 

 cats per family was about one. Allowing one cat 

 per family throughout the country would give a to- 

 tal of 4,700,000 cats kept by these families. If we 

 assume that the farm cat in good hunting-grounds 

 kills ten birds a year, we may assume that the 

 town cat, under less favorable conditions, aver- 



