Note 1 — Front matter

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.