2 BULLETIN 1165, U. S. DEPARTMENT OF AGRICULTURE. 



The work has been continued, but unfortunately on a smaller 

 rather than a larger scale. During the war many persons were 

 unable to make the necessary surveys and some lost interest be- 

 cause of the impossibility of publishing the results obtained. The 

 returns for 1919 were so few as to be of value for purposes of comparison 

 only, in those cases where the areas dealt with were previously, or 

 subsequently, reported upon. A gratifying increase in interest and 

 in the number of returns was shown in 1920. 



For these seven years the bird censuses taken in the part of the 

 country north of Maryland and east of Kansas have been sufficient 

 in number to allow some generalizations as to the average bird 

 population, but many more are needed from the Southern and 

 Western States before it will be possible to draw any conclusions as 

 to the bird life of these sections. 



The counts of 1911 and 1915 showed slightly over one pair of birds 

 to the acre on the farm land of the northeastern section above men- 

 tioned, or approximately 800 pairs to the square mile. For the five 

 years 1916 to 1920, inclusive, there are fewer reports than for the 

 two earlier years, but the averages obtained agree fairly well with 

 those previously published, so that it seems provable that the figures 

 above stated are reliable. As 3 r et nothing can be said about the num- 

 bers of the individual species, and only tentative statements are 

 possible regarding the relative abundance of a few of the most common 

 species. 



Many problems concerning bird life can be solved by no other 

 means than by bird censuses; that some can be solved, in part at 

 least, by this work has alreadv been proved, but many have not yet 

 even been touched upon. How many birds per acre breed in the 

 different parts of the country, in the permanent marshes, and in 

 the forested regions of New England, the eastern mountains, and 

 the Rockies ? What is the relative abundance of the different species 

 in the country as a whole and in the different life zones, and how are 

 they distributed? Where are the centers of abundance for birds 

 generally and for the several species? Are birds most abundant 

 where they are most needed, about the farms, gardens, and orchards ? 

 How do altitude and latitude affect the numerical distribution of 

 birds ? What effect on bird life has the presence of water, as a small 

 stream or a river, a pond or a lake ? What fluctuations take place 

 in bird life from year to year, or over longer periods? When pro- 

 tection and encouragement bring about an increase in the number 

 of birds nesting on a given tract, are there actually more birds in 

 the locality, or is this increase due to a concentration of the 

 birds from a larger area for nesting purposes ? How do birds 

 respond to changes in such environmental conditions as more intensive 

 cultivation, changes in crops, or the clearing of woodland ? How 

 is irrigation affecting the bird life of the arid lands of the West? 

 What changes will occur there in numbers and species, and how 

 rapidly will they take place ? How much have birds increased under 

 protection? Are the present Federal and State laws adequate? 

 What changes, if any, are taking place in the numbers and relative 

 abundance of the several species? 



That the counts might be made in a uniform way and thus pro- 

 vide data which could be used in comparisons and in deducing the 

 desired information, each observer was given instructions regarding 



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