8 BULLETIN 187, IT. S. DEPARTMENT OF AGRICULTURE, 



consequence is that after 14 years of bird protection and encourage- 

 ment, these 40 acres support 157 pairs of birds, or about 4 pairs to the 

 acre. 



POSSIBLE TO INCREASE NUMBER OF BIRDS. 



It is evident from the foregoing statement that double the present 

 bird population is easily obtainable, while a threefold increase is well 

 within the possibilities. 



The maximum census just cited of 4 pairs of birds to the acre does 

 not by any means represent the largest number of birds that can be 

 supported on a given area. In the summer of 1914, the 40 acres com- 

 prising the southern end of the National Zoological Park, at Wash- 

 ington, D. C, harbored 164 pairs of birds of 50 species — a notably 

 large variety and a numerous population. Two blocks on the out- 

 skirts of Kenilworth, 111., containing 15 acres, were reported to con- 

 tain 84 pah-s of birds. A section of five blocks at Chevy Chase, Md., 

 covering 23 acres, showed a bird population of 148 pairs — nearly 7 

 pairs per acre. As this is the highest score reached in the census this 

 tract will be treated more fully farther on in this bulletin. 



But bird life can become even more abundant under proper condi- 

 tions. On a 50-acre tract at Viresco, Va., where the birds have been 

 strictly protected during the last seven years, exact censuses show a 50 

 per cent increase in the birds during the past four years. On the 3 

 acres containing the house, 15 pairs nested during 1914. On 1 J acres 

 about a city home at Cranston, K. I., 8 pairs of birds nested in 1914 

 where 12 pairs had nested in 1910, and the owner claims that cats are 

 mainly responsible for the decrease. A field of 2 acres at Nevada, 

 Iowa, on which was growing a variety of tree and bush fruits, as well 

 as hardwoods, evergreens, and shrubbery, had been found and ap- 

 preciated by the birds, as evidenced by 22 pairs nesting there. At 

 Kenilworth, 111., in the midst of the 15-acre tract previously referred 

 to, stands a house whose owner " believes in befriending the wild 

 birds — our friends and neighbors," and as a consequence, in 1914 his 

 yard of half an acre had 9 pairs of birds. 



RECORD FOR DENSITY OF POPULATION. 



The census at Chevy Chase, Md., showed the highest number of 

 birds per acre of all the censuses so far reported to the Biological 

 Survey. Here the owner of a half-acre yard, which was well sup- 

 plied with trees and shrubbery, had put up nesting boxes and pro- 

 vided a bird bath, and was rewarded with a nesting population of 13 

 pairs of birds. 



The census area consisted of about five blocks, selected from the 

 most populous part of the village. These ranged from "3 to 6 acres 

 in size and were all occupied by houses, from 5 to 10 houses to 



