Birds of a Maryland Farm : a Local Study of Economic Ornithology
1902
Judd, Sylvester D. |
Merriam, C. Hart (Clinton Hart) |
The principal method used by the Biological Survey in investigating the food habits of birds is an examination of the contents of stomachs, the material for which is obtained from all parts of the United States. In case of each species the separate data accumulated by examining as many stomachs as possible are tabulated and show the food of the bird in question to consist of various proportions of certain elements.