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



FUTURE WORK. 



The bird census work must be carried on through many years and 

 on a much larger scale if exact data are to be accumulated on which 

 to base definite comparisons for determining what changes are taking 

 place in the bird life of the country and whether these changes are 

 local or general. The data now at hand indicate that on a given area 

 where birds are protected the number breeding will gradually increase 

 from year to year; but how long this will continue and what will occur 

 when the maximum density is reached can not yet be determined. 

 Previous to the destructive season of 1917, the results of which were 

 so apparent in the censuses of 1918, there had been a gradual increase 

 in the number of birds per acre on many tracts in the eastern United 

 States, and following this setback birds are found to be again on the 

 increase. 



Long series of exact records, such as this work will provide, will 

 indicate whether the birds in the country as a whole or in certain 

 localities are increasing or decreasing; or whether following periods 

 of increase, setbacks such as the unfavorable season of 1917 tend to 

 keep the average over a period of years approximately the same. 

 From the work thus far done, it seems that over a long period changes 

 may be expected in the distribution and relative abundance of certain 

 species, rather than in the total number of birds in the country. On 

 some tracts, little change in the number of birds is apparent from year 

 to year, while on others an increase is shown, and on still others a de- 

 crease. Are such changes due to local conditions or are they part 

 of definite changes that are taking place in the bird life of the country ? 



With bird censuses continued }^ear after year, a large amount of 

 increasingly valuable data will be accumulated, from which much 

 can be learned regarding the bird life of the country and the changes 

 that take place. Each year's records add to the value and useful- 

 ness of those already on file. Many problems are presented by the 

 material now in hand and new problems are brought out by each 

 year's w T ork, for the solution of which we must look to the future. 



