Determination of Sex in Birds.—To a collector who is working under difficulties this often seems like the very "last straw upon a camel's back;" but it must be attended to in every case wherein the sex of the bird is not clearly and unmistakably indicated by the plumage. If you can, get an experienced ornithologist to show you how to determine the sex in difficult subjects (e.g., young birds, or birds midway between two breeding seasons). But there are ways in which we can help ourselves. If you begin with birds during or near the breeding season, you will have plain sailing long enough to become familiar with the subject.
In birds the organs of generation lie close up to the lumbar vertebræ, near the kidneys, in the region called "the small of the back." The best way to reach this region for examination is to make a cut clear across the wall of the abdomen, break the back over at the last pair of ribs, and the intestines will at once fall down, exposing the lumbar region. You will then see the kidneys—two large, dark-brown masses situated in the concavity of the sacrum—and on their surface, at the upper end, lie the reproductive organs. The testicles of the male are two dull, whitish, ellipsoidal, or nearly round bodies, of the same size, lying close together. The sign for this sex is the astronomical sign for the planet Mars ♂.
The ovary of the female is, except during the breeding season, the most difficult to distinguish. Look first for a little bunch of minute round globules, of varying sizes and grayish white color. In the breeding season the eggs are easily found. Failing in that, you must look for the ovary itself, which, when found, will be recognized as a little, irregular, flattish bunch of a light gray color. If you search with a magnifying-glass, you may be able to detect it by its peculiar granulated appearance. The sign for the female is the sign for the planet Venus ♀.
[CHAPTER VII.]
COLLECTING SKINS OF LARGE BIRDS.
General Principles Involved in Skinning Large Birds.—In skinning a large bird you must have room according to your strength and the size of your subject. You will need the usual materials in quantity, plenty of table space, and a stout hook depending from the ceiling at the end of a stout cord, to hang your half-skinned victim upon at a certain stage of the proceedings.
With but few exceptions, the process in skinning a large bird is, from start to finish, precisely similar in principle to that for a small one, which has already been described. When you get the body about half skinned, and are well started up the back, thrust your hanging hook into the top of the pelvis, and suspend the bird in mid-air, so that you can work with both hands. Be careful, however, throughout the whole operation that you do not allow the weight of the body of the skin to stretch the skin of the neck.
If the head is small enough that the skin of the neck will pass over it, skin right over it to the base of the beak itself, and proceed in every respect as with small birds. If, however, the skin of the neck will not go over the head, then skin the neck as far toward the head as you possibly can (usually in such cases you can go no farther than the lower end of the axis or second cervical vertebra), and then cut it off.
The next step is to skin the head. Turn the skin right side out, make a clean, straight cut from the top of the head straight down the back of the neck for a sufficient distance to allow the remaining cervical vertebræ to be drawn up through the opening. It is now a very simple matter to skin the head and clean the skull.