28 CATALOGUING AND LABELING. 
     
    
   
   
    
     tinguished by their color, but the young male frequently resembles 
     
     the female, while in some instances the female has been known to as- 
     
     sume the plumage of the male. Dissection, therefore, is the only safe 
     
     way to determine sex. Upon reaching stage 36, in the operation of 
     
     making a birdskin, cut through the left side of the body from the 
     
     vent to the neck, taking care not to, disturb the internal organs. Force 
     
     the edges of the opening apart, and, pressing the intestines gently to 
     
    
   
   
    
       
     
    
   
   
    
     Fm. 1.—A completed birdskin. (Reduced). 
     
    
   
   
    
     one side, look for the sexual organs, which will be found on the walls 
     
     of the small of the back very near to the backbone. The male organs 
     
     (testes), two in number, are usually dull-white, elongate bodies lying 
     
     side by side. The female organs (ovaries) are composed of numerous 
     
     round bodies lying in a mass or cluster. In the breeding season the 
     
     sexual organs of birds become much enlarged, and at this season the 
     
     testes of a male Chipping Sparrow are about the size of a pea, while 
     
     the ovaries of the female have been likened to a bunch of grapes, the 
     
     largest being the size of the yolk of the egg of this species. After the 
     
     breeding season the sexual organs decrease in size, and in adults in the 
     
     winter and young birds are sometimes difficult to find. The testes of 
     
     a male Chipping Sparrow at that season are about as large as a small 
     
     pinhead, while a hand-lens is required to plainly distinguish the ova- 
     
     ries of the female. The arrow of Mars ( s ) is used to indicate the male 
     
     sex; the mirror of Venus ( 52 ) the female sex. 
     
    

    
     Cataloguing and Labeling—Before skinning your birds you should 
     
     catalogue them. The catalogue should have columns giving (1) the 
     
     date, (2) your serial collection number, (3) name of the bird, (4) 'sex, 
     
     (5) place of capture, (6) name of collector, and (7) remarks. In the last 
     
     column enter any notes on the color of the eyes, or parts which will 
     
     change color when drying, contents of the stomach, and other notes. 
     
     In addition to this “ day-book” or “blotter ” some ornithologists open 
     
     a ledger account with their collection, and devote a folio to each spe— 
     
     cies Where are posted the entries made in the collection register. 
     
    

    
     Labels should be of strong bond paper, two inches and a half long 
     
     and half an inch wide. They are attached to the crossed legs of the 
     
     bird by linen thread strung through their left end. The face of the 
     
     label bears the name and sex of the bird, place and date of capture.