ECONOMIC VALUE OF BIRDS TO THE STATE. 23 



How A Bird's Value to Man Is Ascertained. 



To learn with scientific exactness the nature of a bird's food and then to deter- 

 mine whether it is an injurious or beneficial species requires especial training on the 

 part of the investigator. He must not only be an ornithologist but he must also 

 have a knowledge of botany and entomology. Three methods are employed by 

 the economic ornithologist in studying a bird's food: (i) The bird may be caged in 

 order that its dislikes, likes, and preferences, as well as the quantity of food it will 

 consume in a given time may be ascertained ; (2) the bird may be studied in 

 nature, and (3) the contents of a bird's stomach may be examined. The last- 

 named method yields by far the most definite and satisfactory results and is the 

 one most frequently employed. While the individual student may, unassisted, 

 make the best use of his opportunities to learn the character of a bird's food, the 

 food habits of a species can be properly determined only through the analysis of a 

 large number of stomachs taken at places throughout its range and representing all 

 the seasons. Our most important investigations into the food habits of birds have, 

 therefore, been made by specialists in the employ of the State who could secure the 

 co-operation of others. Economic ornithologists representing the States of Illinois, 

 New Hampshire, Massachusetts, Pennsylvania, Wisconsin, and Nebraska have con- 

 tributed largeh' to our knowledge of the food habits of birds, but for the greater 

 part of our exact knowledge of the economic value of our birds we are indebted to 

 the Biological Survey of the U. S. Department of Agriculture at Washington. It 

 is from the sources just mentioned then, and especially from the publications 

 of the Biological Survey, that the following facts, based in the main on stomach 

 examinations, are taken : 



Statistics of Pood Habits. 



WATER BIRDS. 



As yet practically no systematic study has been made of the food of water birds. 

 It is known, however, that Gulls are of great service as scavengers feeding on 

 aquatic animals which, in dying, come to the surface. The truth of this statement 

 was very forcibly impressed on my mind, when, some years ago, I visited the lower 

 harbor of New York Bay to see the Gulls which were attracted there by the garbage 

 which each day at high tide was deposited on the water by the scows of the Street- 

 cleaning Department of New York City. The number of Gulls present on this 

 occasion was beyond calculation, but certainly exceeded three hundred thousand. 

 Before the scows began to discharge their cargo most of the birds were resting on 



