14 THE MIGRATIONS OF BIRDS 



to notify the Biological Survey to learn the source of 

 the marker. In this way many thousands of bands 

 have been used, and returns have come from many 

 hundreds. At the present time the work of bird- 

 banding has become so widespread and popular that 

 four regional associations of interested persons have 

 been formed in the United States and Canada, to 

 consolidate the work by geographic areas. 



During development of this work attempts at 

 banding birds were directed first mainly to the 

 marking of nestlings, but in the last few years this 

 has been supplemented and largely replaced by the 

 use of traps for the capture of grown individuals. 

 The marking of nestlings, while fruitful, has many 

 disappointments, since mortality among young 

 birds during the fledgling period, before they are 

 sufficiently alert to escape their many enemies, is 

 so heavy that many bands are wasted. Trapping 

 methods at present used were developed early by 

 Mr. S. P. Baldwin, and have attained a high degree 

 of efficiency. The trap is especially valuable since it 

 does not injure the bird and enables consecutive 

 records of the same individual. The method has 

 been extended until now trapping devices are made 

 for the capture of species of the most diverse form 

 and habit. 



The great value of bird-banding to the student of 

 migration lies in the data that it affords on the move- 



