HISTORICAL REVIEW 
A review of the progress which has been made in the study of North 
American birds during the eighteen years since the first edition of the 
“Handbook” was published must impress one with the fact that it is 
our knowledge of living rather than of dead birds which has increased. 
A more exact discrimination, larger and better collections, and 
gradually changed standards as to the degree of differentiation which 
deserves recognition by name, have added many forms to our “Check- 
List,” and rendered more definite our knowledge of the relationships 
of others. Particularly is this true of the birds of the Pacific coast 
region. This systematic work has appeared in various special papers 
and monographs, the most thorough of which, not only for the period 
under consideration, but for any preceding period in the history of 
North American ornithology, is Ridgway’s “Birds of North and Middle 
America,” of which five volumes have thus far been issued. 
Thanks to the American Ornithologists’ Union, our nomenclature 
has been revised with the utmost care and, while the numerous result- 
ing changes in names may be annoying to present-day students, those 
who follow us will enjoy, in greater measure, that stability which is 
the ideal of the biologist. The third (1910) edition of the Union's 
“Check-List’”’ contains this modern nomenclature; but it is worthy of 
note that the classification employed in this work is the same as that 
used in the first (1886) edition of the “‘Check-List.”” So little advance 
has been made in this branch of ornithology that no system of classi- 
fication proposed since 1886 was considered sufficiently satisfactory 
to warrant adoption by the Committee of the Union having in charge 
the preparation of the 1910 edition. 
The studies of Dwight and others have made far more definite 
our knowledge of the molt of birds, the times and manner of feather- 
loss and renewal having been determined for many species, with an 
exactness made possible only by the collecting of specimens for this 
special purpose. At the same time, Beebe, by experiments on captive 
birds, has attacked the problem of the causes of molt, while Strong’s 
histological work on the feather has increased our understanding of 
its growth and development. 
In laboratory experiment on living birds, Beebe has shown certain 
effects of humidity upon the colors of feathers; Davenport has used 
Canaries and domestic fowls in working on the laws of heredity; Porter 
and others have conducted psychological investigations upon certain 
species; and Watson has pursued similar studies upon the Noddy and 
the Sooty Tern in nature. The highly original researches of Thayer 
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