2 BULLETIN 39fi, U. S. DEPARTMENT OF AGEICULTUEE. 



The reports of 1914 from farms of the Northeastern States agreed 

 so well among themselves and with results obtained by other persons 

 in previous years that they seemed to warrant the belief that their 

 average closely approximated the actual facts. The counts of 1915 

 from the same region serve to strengthen this belief and to make it 

 practically certain that the conclusions drawn as to the number of 

 birds on these farms is very nearly accurate. 



A word of explanation may be offered as to just what results were 

 expected from the work, and also as to what phases of the bird popu- 

 lation question are not covered by these first two years of bird 

 counting. 



The most important factor of bird life concerns its relation to 

 human beings and has to do with its influence for good in helping 

 the farmer destroy the foes of his crops. Hence to ascertain the 

 numbers of birds in the trees and shrubbery on the acres actually 

 devoted to crops and immediately contiguous thereto is more im- 

 portant economically than on other lands, and these numbers have 

 been most in mind in the work thus far conducted. The principal 

 question of these two years has been, therefore, What kinds of 

 birds and how many pairs of each kind nest on the farms in the area 

 surveyed and remain on or near them during the middle of the 

 summer, when crops grow fastest and also suffer most from insect 

 enemies ? 



So far as the farms of the Northeastern States are concerned, the 

 average of the 1914 counts was about one pair of birds to the acre, 

 and as this number is so nearly the same as presented by the addi- 

 tional work of 1915, it may be said with reasonable assurance that 

 this is the average bird population of that part of the Northeastern 

 States actually devoted to agriculture. 



The work has not yet reached the stage where the general average 

 found — in the Northeastern States of nearly 800 pairs of birds to the 

 square mile — may be subdivided and an estimate made of the num- 

 ber of pairs of each kind. For some of the commonest and most 

 widely distributed species, like the robin and English sparrow, how- 

 ever, the reports are probably sufficiently numerous to permit an 

 approximate estimate. 



The different kinds of birds on a farm are so much more variable 

 than the average number of birds per acre that it will require many 

 more counts to serve as reliable bases for formulating averages of 

 species. Two contiguous farms of 100 acres each may each support 

 100 pairs of nesting birds, yet the kinds of birds on the two farms 

 may vary widely, according as one farm is upland, and the other 

 lowland; one devoted to grain raising, and the other, in perma- 

 nent pastures, to dairying; one supporting a growth of hardwood 

 trees, the other showing nothing but evergreens. 



