SECOND ANNUAL KEPOBT OF BIRD COUNTS IN THE U. S. 3 



Many phases of bird population have scarcely been touched by the 

 two years' Avork. How many birds to the acre inhabit permanent 

 marshes ? What effect on the number of birds has the presence of a 

 stream, a river, a pond, or a lake ? What is the average effect of alti- 

 tude or latitude on bird life? These and many other questions are 

 interesting and important, but may not yet be answered. 



Another important question concerning bird population, which is 

 partially covered by the counts of 1914 and 1915, relates to the num- 

 bers of birds inhabiting those areas near large centers of human 

 population which are not devoted strictly to agricultural purposes, as 

 city lots, parks, cemeteries, etc. It is, of course, desirable to have the 

 greatest possible numbers of native birds in all such places, and some 

 of the returns show in a very striking manner how ^quickly and 

 abundantly the birds respond to efforts to make these sections better 

 adapted to a large bird population. 



A brief explanation should be made regarding the qualifications 

 needful in an observer to result in a satisfactory enumeration. 

 The Biological Survey has for many years had several hundred mi- 

 gration observers throughout the country reporting bird arrivals and 

 departures. If a person is familiar with only half a dozen of the 

 commonest birds and is well situated to note the earliest arrivals 

 among these species, his notes on the birds he knows are just as 

 valuable, so far as they go, as those of one who has a wider bird ac- 

 quaintance. But in counting birds such partial knowledge is worse 

 than useless. If a bird count is to have value, it must be true not only 

 as far as it goes, but it must tell the whole truth. This requires that 

 the enumerator be able to identify with certainty all the birds nesting 

 on the area he covers, or be able to give a recognizable description of 

 those he is unable to name. Lack of such knowledge has made un- 

 usable some reports which were undoubtedly correct as to the species 

 listed, but which showed their incompleteness by absence of records 

 for the smaller and less conspicuous birds. 



Letters of criticism of the method used for counting the pairs of 

 birds have been received. Of course if one is living on the area on 

 which he reports and has the time and inclination to go over the 

 ground repeatedly, day after day, until each nest has been actually 

 located, his report would be more accurate and valuable than one 

 made by ear by the method outlined in the circular of instructions. 

 But this would require twenty to fifty times as many hours' observa- 

 tion, and hardly more than one person in a hundred would feel in- 

 clined or be able to devote so much additional time to the work. Some 

 six years of such work done by the writer convinced him that a person 

 who knows the birds by their songs can use the method advocated 

 and obtain, with the expenditure of a minimum of time and effort, a 

 count that will compare favorably in accuracy with the most pains- 



