A SECTIONAL BIRD CENSUS. 



Taken at Berwyn, Chester County, Pennsylvania, 

 During the Seasons of 1899, 1900 and 1901. 



With a better understanding of geograpliical distribution it 

 becomes desirable, in local lists at least, that a more accurate 

 estimate of the bird population should be employed than the 

 usual expression of indefinate terms. The time-honored 

 phrases, however admirably giaduated, often utterly fail to give 

 a clear idea of the numerical status of a species, and are useless 

 for comparative purposes generally. On the other hand a bird 

 census of a not too restricted area accomplishes at least two de- 

 sirable objects: It forms a reasonably accurate basis for com- 

 parison with similar tracts, or future enumerations over the 

 same ground reveals the rate of increase or decrease; and it 

 enables an approximation of the total bird life to be made of a 

 larger section. 



The writer does not plead any special qualifications for the 

 work other than that the locality has been most familiar ground 

 for the past twenty years. The task was not light and the 

 manner of accomplishing it varied according to circumstances. 

 Thus, while the discovery of a tenanted nest was considered 

 final and conclusive evidence of residence, the exact location of 

 every nest was deemed impossible without unlimited time and 

 energy. The many little traits, so well known to the oologist, 

 indicating the nearby habitations; repeated horizons; the cor- 

 roborative evidence in the shape of the empty nests exposed by 

 the falling leaves; all figured to a greater or lesser extent in the 

 final count, with a constant leaning toward conservatism. 

 Much time was consumed in amassing the necessary data, es- 

 pecially during the last two years. The enumeration was 



