METHOD OF EXAMINING STOMACHS. 27 



By careful experiment with living Grows — either caged or tame — 

 many interesting points may be determined, though the natural appe- 

 tite and food of a bird can not always be determined from the study of 

 partially domesticated individuals. There remains but one method of 

 study which promises anything like uniformly good results, namely, 

 the examination of the actual contents of the stomachs of Crows. 



For many years the division has been collecting Crow stomachs from 

 every part of the country and at all seasons of the year. This collec- 

 tion numbers more than 900, most of which were taken' in summer. 

 As the examination of these stomachs has been supplemented by a 

 large quantity of material from the winter roosts, it is believed that 

 the data at hand are ample for the settlement of all the important 

 questions relating to the food of Crows. In collecting these stomachs 

 the utmost care has been taken to preserve all data that might throw 

 light on the habits of the bird or in any way assist in the identifica- 

 tion of the contents of the stomach. In most cases the following facts 

 have been recorded: (1) Sex and age; (2) date of capture; (3) hour of 

 capture; (4) town, or at least county, where killed; (5) character of 

 actual place where killed; (6) name of collector; (7) remarks as to 

 place of killing, occupation of bird when killed, character of crops in 

 vicinity, and abundance of any particular food. 



METHOD OF EXAMININGr STOMACHS. 



Since the determination of the various ingredients of the stomach 

 contents is not always a simple matter, a description of the method 

 pursued may be of interest. A few stomachs are obtained fresh, but 

 the great majority received in the laboratory are preserved in alcohol. 

 The process of examination, however, is essentially the same in both 

 cases. A stomach is cut open and by means of a jet of water the con- 

 tents are washed into a dish; then more water is added. Any con- 

 spicuous insects or large pieces of food that float are picked out and 

 allowed to drain on blotting paper. The water covering the remainder 

 is poured upon a filter and replaced by fresh water, which in turn is 

 decanted upon the filter, and the process continued until the water 

 remains clear and most of the lighter material has been removed. The 

 coarser material is now spread out thinly under water and examined 

 with a hand lens. By tilting the dish from side to side most of the 

 sand or gravel can be separated and this is collected on a blotter by 

 itself. The remaining coarse or heavy material is thoroughly examined 

 with a magnifier. The seeds and grain are picked out and placed by 

 themselves, also the bits of bone, shell, and the hard x>arts of insects. 

 Sometimes this results in the separation of a dozen or more little heaps, 

 each composed of one kind of material, and these heaps are arranged 

 in three groups, composed respectively of animal, vegetable, and min- 

 eral matter. The mineral matter is examined for bits of shell, teeth of 

 fish, reptiles, or mammals, and small, heavy bones, which often give a 



