The Assessment of the Food of Birds*

Summary. Qualitative knowledge of the food of many birds is fairly complete, but on the quantitative aspects of the problem there is little exact information. The materials available for the study of bird foods include not only stomach contents and pellets, but also dung, the rejectamenta of meals, accumulated stores, the field notes of observers and photographs. The sampling in many studies has been irregular or inadequate. In a number of species the collection of statistically satisfactory samples of stomach contents from any one locality or habitat may be impossible. Foods may be assessed by frequency of occurrence, by enumeration, by weight or by volume. The weights or volumes may be measured “as found” or by approximations to the weight or volume of the food at the time of ingestion. There is no one ideal method, and the food of each species or group of species should be investigated and assessed by the methods which seem to be most appropriate. Published records and summaries should be in such form that they can readily be combined with the results of other investigations. The lack of fundamental ecological knowledge makes it impossible to pronounce upon the “economic status” of any species, save in a few very obvious cases.