70 



Bird - Lore 

 FALL MIGRATION, Continued 



The "Data in the Biological Survey" 



Explanatory note by PROFESSOR COOKE 



IT may interest the readers of Bird-Lore to learn something about the 

 sources of the notes on migration that appear from month to month. The 

 Biological Survey was established twenty-five years ago, and part of its 

 work from the outset has been the accumulating of data on bird distribution 

 and migration. The card system is used and each note is entered on a separate 

 card. At the present time the "data in the Biological Survey " are contained on 

 about four hundred thousand cards of unpublished notes derived principally from 

 the more than two thousand different migration observers who have contributed 

 their reports during these twenty-five years. The remainder is derived from 

 records of museum specimens and from the field notes of the staff of the Bio- 

 logical Survey. 



These original notes are supplemented b}- many published records. The most 

 important ornithological publications have been extracted thoroughl\-, and 

 many notes gathered from the so-called minor publications. About two hundred 

 thousand cards of published records are now on hand. The notes from 'The Auk ' 

 a'one required over forty thousand cards. 



The Biological Survey, therefore, has about six hundred thousand notes from 

 wliich to draw for information concerning the distribution and migration of North 

 American birds. It follows that on some of the more common birds the records 

 must be very voluminous. The migration dates given in this number of Bird- 

 Lore for the Song Sparrow are selected from more than three thousand notes — 

 which, if published in full in the most condensed form, would require more than 

 forty of Bird-Lore's pages. The records for Chicago occupy only two lines, one 

 for arrival in spring and the other for departure in the fall, but these dates are 

 selected from 83 records contributed during 26 years by 28 dift'erent persons. 



