12 BIRDS TX THEIR RELATIONS TO MAN. 



fying the food of hawks and owls. A simple magnifier will 

 be needed constantly and at times there will be use for a com- 

 pound microscope. 



Instead of examining- each bird at the time of its capture, 

 it is usually more convenient to remove the digestive tract, 

 and, after attaching a numbered tag by means of thread, to 

 put it into a jar of five per cent, formalin or eighty per cent, 

 alcohol, where it may safely remain until enough have ac- 

 cumulated for a day's work. Viscera may be kept indefi- 

 nitely if the preservative fluid is changed as often as it be- 

 comes discolored. The number on the tag corresponds to 

 one in the note-book, where are recorded the name of the 

 bird, the date and place of capture, and any other data that 

 may have a bearing on diet. 



When ready for the analysis, a stomach may be cut open 

 wilh a pair of scissors or a scalpel, and the contents emptied, 

 with a little water, on a piece of plain glass, — say, three by 

 three inches, for any bird smaller than a flicker. If a dis- 

 secting microscoi)e be available, the magnifier may be managed 

 more easily, and, furthermore, transmitted light or reflected 

 light with a black or white background may be used at will. 

 AVlth a pair of sharp needles set in handles the mass may be 

 spread over the glass and assorted. Wings of insects may be 

 unrolled and floated on tlie film of water so as to be identified 

 as to family and often as to genus. By assembling the parts 

 of insects or other food of the same kind into little piles, the 

 relative amount of each may be estimated. 



Hawks, owls, crows, flycatchers, and certain other birds that 

 devour indigestible matter, such as bones, the elytra of bee- 

 tles, etc., regurgitate such matter in the form of compact 

 pellets, generally at the roosting places.^ Insectivorous and 



^ See The Common Crow, Bull. No. G, U. S. Dept. of Agr., Div. Orn. 

 and Mam.; also Montgomery on tiie Food of Owls, Am. Nat., July, 1899, 

 vol. xxxiii. pp. 568-57:^. 



