PKELIMINAEY CENSUS OF BIKDS. 3 



United States Department of Agriculture, 



Bureau of Biological Survey, 



Washington, D. C, April 25, 1914. 



Dear Sir: The passage of the Federal law placing migi-atory game and insectivorous 

 birds in charge of the Department of Agiiculture makes it desirable to obtain more 

 detailed and definite information concerning the distribution of bird life in the United 

 States, and for this data we must look mainly to voluntary observers. This bureau 

 desires to obtain a series of bii'd censuses, beginning with this summer (1914), taken 

 during the breeding season, with a view to ascertaining how many pairs of each species 

 of birds breed within definite areas. Such censuses will serve as a basis for determin- 

 ing later whether the present State and Federal laws are effective and whether game 

 and insectivorous species are increasing or diminishing in numbers. In this under- 

 taking you can materially aid by taking a census of the birds breeding this summer 

 on some area or areas selected to faii-ly represent the average character of the country 

 in your immediate neighborhood. The ideal tract of land would be one that exactly 

 represents the average conditions of the neighborhood in the proportions of wood- 

 land, plowed land, meadow, etc., contained in it. As this idea is practically unat- 

 tainable, an area should be selected representing fairly average farm conditions, but 

 without woodland . It should not be less than 40 acres — a quarter of a mile square — nor 

 more than 80 acres, and should include the farm buildings, with the usual shade 

 trees, orchards, etc., as well as fields of plowed land and of pasture or meadow. 



The area should be selected not only with reference to the present summer's work, 

 but should, if possible, be chosen so that the physical conditions will not be much 

 changed for several years; if succeeding annual censuses show changes in the bii'd 

 population, it will be known that they are not due to changed environment. 



What is wanted is a census of the pairs of bii'ds actually nesting within the selected 

 area. Birds that visit the area for feeding purposes should not be counted, no matter 

 how close their nests are to the boundary Unes. 



It is practically impossible to take this census on the scale of 40 to 80 acres in a 

 single day. A plan which has been used with advantage for several years is to begin 

 at daylight some morning the last of May or the first week in June and zigzag back 

 and forth across the area, counting the male birds. Early in the morning at that 

 season every male bird should be in full song and easily counted. After the migra- 

 tion and the birds are settled in their summer quarters each male can safely be taken 

 to represent a breeding pair. 



The census of one day should be checked and revised by several days of further 

 work, in order to insure that each bird seen is actually nesting within the area and 

 make certain that no species lias been overlooked. 



The height of the breeding season should Vje chosen for this work. In the latitude 

 of Washington — latitude 39° — May 30 is about the proper date for the original census. 

 In the latitude of Boston the work should not begin for a week later, while south of 

 Washington an earlier date should be selected. 



The final results of the census should be sent to this bureau about June 30 and 

 should be accomj^amed by a statement of the exact boundaries of the selected area, 

 defined so explicitly that, it will be poH.siblo 25 years hence to have the census repeated. 

 The name of the present owner of the; land should be given, together with a careful 

 description of its character, including a statement whether the area is dry upland 

 or moi.st bottom land, the number of af-res in each of the principal crops, or in per- 

 manent meadow, pasture, orchard, ffwamp, roads, etc., the kind of fencing used, and 

 whether there is much or little brush along any fences, roads, or streams, or in the 

 jKjrmanent pasture. 



If there is an isolated piece of woodland conveniently near and comprising 10 to 

 20 acres we .should like to have a separate census made of the birds nesting therein. 



