SKINNING BIRDS. 41 



secondaries ; and also when a specimen is to be 

 mounted, the eye cavities should be filled with clay 

 well kneaded to the consistency of putty. 



Section III. : Ascertaining the Sex of Birds. 

 — Although the sex of many birds can be ascer- 

 tained with tolerable certainty by the plumage, 

 yet this is never an infallible guide, and to make 

 perfectly sure of every case the interrfal organs 

 should be examined. I always advise dissecting 

 such plainly-marked birds as scarlet tanagers or 

 red-winged blackbirds, and by practising this habit 

 I was once fortunate enough to discover a female 

 painted bunting in full male livery. The sex of 

 birds can be readily ascertained in the following 

 manner : Lay the bird's body on its left side, with 

 the head from you ; then with a knife or scissors, 

 cut through the ribs and abdominal walls on the 

 right side ; then raise the intestines, and the organs 

 will appear. 



In males, two bodies, the testicles, more or less 

 spherical, will be seen lying just below the lungs on 

 the upper portion of the kidneys (Fig. 6, 3, 3). These 

 vary not only in color from white to black, but also 

 in size, depending upon the season or age of the 

 the specimen. Thus, in an adult song sparrow, 

 during the beginning of the breeding season, the 



