x HISTORICAL REVIEW 
have greatly stimulated interest in the study of the colors of birds in 
relation to their environment. 
Dealing still with the more technical branches of ornithology, the 
investigations of Fisher, Beal, and other members of the Biological 
Survey of the United States Department of Agriculture, of Forbush 
in Massachusetts, and of other state ornithologists, have supplied by 
far the larger part of our exact knowledge of the food-habits of our 
birds and determined for the first time the economic status of many 
species. This work constitutes one of the most pronounced and impor- 
tant phases of research during the period under consideration. While 
based, primarily, on field work in observing as well as in collecting, 
special training in laboratory methods is required to make the analyses 
of stomach contents, from which, in the main, the nature of a bird’s 
food is ascertained. 
Field, as well as laboratory work, has also been required to produce 
the faunal papers and books which, in volume, form the greatest addi- 
tion to the ornithological literature of the past decade and a half. From 
the pioneer explorations of Merriam, Fisher, Nelson, Bailey, Preble, 
Osgood, and other members of the Biological Survey, in new or but 
" little-known regions, to the almost final reports of Brewster and others 
on the bird-life of localities which have been studied for years by many 
observers, these publications have added enormously to our knowledge 
of the distribution of North American birds. This is particularly true 
of western North America, especially of the Pacific coast region, where 
Grinnell, W. K. Fisher, Swarth, and other members of the Cooper 
Ornithological Club, have placed on record a vast amount of data 
concerning the birds of this area. 
Besides furnishing material for the more philosophic phases of 
faunal work, these monographs and local lists often treat also of the 
migration of the birds with which they deal. Most important contribu- 
tions to this subject have been made by the large and widely distributed 
corps of observers acting under the direction of the Biological Survey, 
which, under the authorship of Cooke, has published several important 
bulletins on migration. Here also should be mentioned the significant 
experiments of Watson upon the homing instincts of Terns, which are 
referred to beyond (p. 54). 
Possibly, in no other branch of definitely directed ornithological 
research has greater advance been made than in the study of the nesting 
habits of birds. For the first time in the history of ornithology, trained 
biologists have devoted an entire nesting season to the continuous 
study of certain species, and the results obtained by Watson, Herrick, 
Finley, and others, have, in a high degree, both scientific value and 
popular interest. 
No small part of the educational value of work of this kind is due 
to the photographic illustrations by which it is usually accompanied, 
and bird study with a camera may be said to be the most novel and, 
in many respects, the most important development in ornithological 
