98 THE FOOD OF BIRDS 
Tue Foop or Birps 
. Food and Distribution 
Food and Habit 
Economic Value of Birds 
Birds and Insects 
Birds and Weeds 
Birds and Rodents 
Birds as Scavengers 
Food and Distribution.—Birds consume a large amount of food and 
they rarely store it. No one factor, therefore, exercises a greater or 
more constant influence on their activities than the ever-present neces- 
sity of securing a sufficient amount of the proper kind of nourishment. 
Not only are a bird’s daily movements more or less governed by 
the search for food, with pronounced local variations in numbers, due 
to the ripening of fruits, unusual abundance of insects, supply of car- 
rion, etc., but the presence or absence of the species during certain 
seasons may depend directly on the abundance or scarcity of a certain 
kind of food. Given bayberries, and one may expect Myrtle Warblers 
to winter in numbers near New York City; buckwheat in a pile of 
chaff induced a flock of Mourning Doves to pass the winter at Engle- 
wood, N. J.; the failure of the coniferous seed crop is evidently the reason 
for the irregular occurrence of great numbers of Crossbills south of their 
usual winter range, to cite only a few of the innumerable instances 
showing how both the local and general movements of birds are influ- 
enced by the food-supply. 
Food and Habit—From the Swifts, coursing the sky almost be- 
yond the reach of vision, to the Diver beneath the waters, birds neglect 
no spot containing food. The result is not only great diversity of fare, 
but a correspondingly wide range in the methods, or feeding habits, 
by which it is secured. (See under Uses of the Bill and Feet.) 
Economic Value of Birds.—Interesting as we shall find the study 
of a bird’s food in relation to its distribution and habits, it is of even 
greater importance for us to learn in what way or ways the nature of 
its food determines its economic relations to man. 
In no branch of American ornithology has greater advance been 
made, during the past twenty years, than in the study of the value of 
birds to man based on a knowledge of their food. This is due chiefly 
to the investigations of the Biological Survey of the United States 
Department of Agriculture, and also to the researches conducted by 
certain states, notably Massachusetts, New Hampshire, and Pennsyl- 
vania. The subject is too wide and too important to be treated ade- 
quately here and the student is referred to the many valuable papers 
listed beyond, particularly to those issued by the Department of Agri- 
culture (many of which can be secured from the Superintendent of 
Documents at Washington) and to Forbush’s “Useful Birds.” 
