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 internal 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 
