Fig. 5.
Section II.: Exceptions to the Usual Method of Skinning.—In case of birds which are very soft on account of having been dead a long time, it may be advisable to open either beneath the wing, making a short incision along the side or above the wing, cutting along the feather tracks just above the scapularies; and some skin ducks through a hole in the back just above the rump. I do not, however, advise such practice, as a rule, as the skins are more difficult to make up, and the bird cannot be mounted quite as readily.
Woodpeckers with large heads and small necks, like the pileated and ivory-billed, and ducks having similar characteristics, as the wood, pintail, and a few other species; also flamingoes, sand-hill, and whooping cranes, cannot be skinned over the head in the usual manner, but the neck should be cut off after the skin has been removed as far as possible, and then a slit should be cut in the back of the head, and the head be skinned through this orifice, but an abundance of absorbent should be used to prevent the feathers from becoming soiled.
Care should be exercised in skinning cuckoos, doves, thrushes, and some species of sparrows, as the skin is not only thin, but the feathers start in the rump and back very readily. Peel the skin off gently, and do not fold it abruptly backward in working on these parts, but hold it as nearly as possible in its original position. The skin of the wood duck, and sometimes that of the hooded merganser, adheres to the flesh of the breast, but it may be separated by working carefully with the back of the knife. In removing the skins of young birds in the down, like ducks and gallinaceous birds, do not attempt to skin the wings.
If a specimen is to be mounted with the wings spread, the secondaries should not be detached, but the knife should be forced down back of the primaries in order to break up the muscles; then as much of the flesh as possible should be removed, and a quantity of preservative pushed in beneath the skin. In larger birds a slit should be made on the under side of the wing, and the muscles removed from the outside without detaching the 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 ascertained 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 specimen. Thus, in an adult song sparrow, during the beginning of the breeding season, the testicles will be nearly or quite a half inch in diameter, whereas in autumn they will not exceed a number eight shot in size; and in nestlings of the same species they are not larger than a small pellet of dust-shot. At this early age, the sex of birds which have become somewhat soft is quite difficult to determine, and the same is true at any season if the specimens be badly shot up. There are other organs, however, in the male. For example, the sperm ducts are always present, appearing like two white lines; and in the breeding season the plexus of nerves and arteries about the vent becomes swollen, forming two prominent tubercles on either side ([Fig. 6], 3, 3).