By Frederick C. Lincoln, _senior biologist, in charge
Section of Distribution and Migration of Birds,
Division of Wildlife Research,
Bureau of Biological Survey_
[Footnote 1: This circular supersedes Department Bulletin 185, Bird
Migration, by Wells W. Cooke, published in 1915. In addition to his
own original investigations in the field and those reflected in the
files of the Biological Survey, the author has made free use of the
writings of Professor Cooke, Alexander Wetmore, William Rowan, A.
Landsborough Thomson, H. A. Allard, and others. To all these grateful
acknowledgment is made, particularly to Doctor Wetmore, Assistant
Secretary of the Smithsonian Institution, who has read the entire
manuscript and made many valuable comments and suggestions.]