Washington, DC: Smithsonian Institution Press, 1930. — 14 p.
Since preparing a classification of North American birds in collaboration with the late W. deW. Miller, of the American Museum of Natural History, for use in the fourth edition of the official Checklist of the American Ornithologists' Union, now in course of publication, the writer has continued investigations in this interesting subject, with the result that he here offers an arrangement of the known birds of the world, living and fossil, in accordance with his present understanding of their relationships. The work of Hans Gadow has been taken as a starting point, and such changes have been incorporated as seem justified from personal research or from the investigations of others. In general, only such variations from the current order have been accepted as seem to be firmly established. Where doubt seems to attach to any proposition, the older classification has been followed; so the following scheme presents a conservative arrangement so far as possible. The list is complete for all categories down to families. Attempt has been made to follow a definite terminology for the various groups, so that there may be no misunderstanding of their proper rank.