Section I.: Ordinary Method.—The only instruments that I use in removing the skin of birds ordinarily is a simple knife of a peculiar form (see Fig. 3); but I like to have a pair of dissecting scissors by me to be used in cases given further on. I also have plenty of cotton, and either Indian meal or dermal preservative at hand to absorb blood and other juices.
Fig. 3.
To remove the skin from the bird, first see that the mouth is plugged with cotton, and if it is, note if this be dry, if not remove it and substitute fresh. It is also well to note if the bird be flexible, for if rigid it is extremely difficult to skin, and it is always best to wait until this peculiar rigidity of the muscles, which follows death in all vertebrate animals, shall have passed. This occurs in warm weather in much less time than in cold, often in one or two hours, but in moderate temperature a bird had better lie for at least six hours after it has been killed. Take then a specimen in the proper condition, lay it on its back on a bench, on which clean paper has been spread, with its head from you, but slightly inclined to the left. Now part the feathers of the abdomen with the left hand, and, excepting in ducks and a few other species, a space, either naked or covered with down, will be seen extending from the lower or costal extremity of the sternum to the vent. Insert the point of the knife, which is held in the left hand, with the back downward, under the skin near the sternum, and, by sliding it downward, make an incision quite to the vent, taking care not to cut through the walls of the abdomen. This can readily be avoided in fresh birds, but not in specimens that have been softened by lying too long. The fingers of the right hand should be employed during this operation in holding apart the feathers. Now sprinkle meal or preservative in the incision, especially if blood or juices flow out, in order to absorb them and prevent them soiling the feathers. Next, with the thumb and finger of the right hand, peel down the skin on the left side of the orifice, at the same time pressing the tibia on that side upward. This will disclose the second joint of the leg, or knee proper. Pass the knife under this joint, and, by cutting against the thumb, cut it completely off, a matter easily accomplished in small birds; rub a little absorbent on either side of the severed joint; then grasping the end of the tibia firmly between the thumb and forefinger of the right hand, draw it outward. At the same time, the skin of the leg should be pressed downward by the fingers of the right hand to prevent tearing. The leg is thus easily exposed, and should be, as a rule, skinned to the tarsal joint. With the thumb-nail, nip off the extreme tip of the tibial bone, and strip the flesh off the remainder of the bone by a downward pull; then give the whole a twist, and cut all the tendrils at once. Of course the flesh may be removed from the bone by scraping, etc., but the above is the best method, and in case of large birds, break the end of the tibia with pliers. Turn the bird end for end, and proceed the same with the other leg, but during both operations the bird should not be raised from the bench. Now peel away the skin about the tail, place the forefinger under its base, and cut downward through the caudal vertebra and muscles of the back quite to the skin, the finger being a guide to prevent going through this. Rub absorbent on the severed portion. Grasp the end of the vertebra protruding from the body, thus raising the bird from the bench; peel down front and back by pushing downward with the hand, rather coaxing the skin off than forcing or pulling it. Soon the wings will appear; sever these where the humerus joins the coracoid, cutting through the muscles from above downward in large specimens, thus more readily finding the joints. Rub on absorbent, and it may be well to remark that this must be done whenever a fresh cut is made. Then the body is laid on the bench, and the skin is held in one hand, or, in large specimens, allowed to rest on the lap or on the bench, but never to dangle. Keep on peeling over the neck by using the tips of as many fingers as can be brought into service and soon, the skull will appear. The next obstruction will be the ears; these should be pulled or, better, pinched out with the thumb and forefinger nails. Do not tear the ears, and special care should be exercised in this respect in owls. When the eyes are exposed, pass the knife between the lids and orbit, close to the former, taking care that the nyctatating membrane be removed from the skin, or it will be in the way when the eyelids are arranged in making the skin. Peel well down to the base of the bill, so that every portion of the skin may be covered with preservative. Push the point of the knife under the eyes, and remove them by a single motion, without breaking them. Cut off the back of the skull at the point shown in the line A, Fig. 4; turn the head over and make two cuts outward as seen at A. A., Fig. 5, thus removing a triangular portion of the skull B, Fig. 4, to which the brain will usually adhere, but when it does not, remove it with the point of the knife. This leaves the eye-cavities open from beneath. Draw out the wings by grasping the end of the humerus in the left hand, and press the skin back with the right, to the forearm; then with the thumb-nail, or back of the knife, separate the secondary quills which adhere to the larger bone from it, thus turning out the wing to the last joint or phalanges. Cover the skin well with preservative, especially the skull, wings, and base of tail; roll up balls of cotton of about the size of the entire eye removed, and place in the cavities in such a condition that the smooth side of the ball may come outward so that the eyelids may be arranged neatly over them. Nothing now remains but to turn the skin back to its former position. Turn the wings by gently pulling the primaries and the head, by forcing the skull upward until the bill can be grasped; then by pulling forward on this, and working the skin backward with one hand, the matter will be accomplished, when the feathers may be lightly smoothed and arranged. It must be borne in mind that the quicker and more lightly a skin is removed the better the specimen will look. By lightly, I mean that the skin should not be tightly grasped nor stretched by pulling. Some workmen will remove a skin from a bird which is nearly spoiled without starting a feather, while others may skin a specimen as quickly, but the plumage will be crushed and broken through rough usage. The time for removing the skin from a small bird should not exceed six minutes, and I have seen it taken off in half this time. Of course the beginner will be longer than this; and then the skin should be occasionally moistened, by using a damp sponge.
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).
In the female the ovaries lie on the right side (Fig. 7, 2) in about the same position as is occupied by the testicles in the male. The ovaries vary in size from that of half the size of an egg to minute points, depending, as in the male, on the season of the year and age of the specimen. In very young birds the ovaries consist of a small white body which under a magnifying glass appears somewhat granular. In both male and female are two yellowish or whitish bodies, in the former sex lying above the testicles, but further forward, and consequently just in front of the kidneys; and in the female they occupy about the same position. In addition to the ovaries in the female, the oviduct is always present (Fig. 7, 3), large, swollen, and convoluted during the breeding season, but smaller and nearly straight at other times. In young specimens it appears as a small white line.
The denuded breast and abdomen seen in birds during the breeding season, cannot always be depended upon as a mark of sex, as this occasionally occurs in males as well as in females.
Section IV.: Preserving Skins.—Taxidermists for many years have made use of arsenic in some form as a preservative; and in the first edition of my “Naturalists’ Guide,” I recommended the use of it dry, stating that I did not think it injurious if not actually eaten. I have, however, since had abundant cause to change my opinion in this respect, and now pronounce it a dangerous poison. Not one person in fifty can handle the requisite quantity of arsenic necessary to preserve specimens, for any length of time, without feeling the effects of it. For a long time I was poisoned by it, but attributed it to the noxious gases arising from birds that had been kept too long. It is possible that the poison from arsenic with which my system was filled might have been affected by these gases, causing it to develop itself, but I do not think that the gas itself is especially injurious, as I have never been poisoned since I discontinued the use of arsenic.
When I became convinced that arsenic was injuring my health, and that of others, I began to experiment upon other substances, and after trying a quantity of various things, have succeeded in manufacturing a nearly odorless compound which has the following advantages over arsenic: It thoroughly preserves the skins of birds, mammals, reptiles, and fishes from decay, and also prevents the attacks of dermestes or anthrenus, while the feathers of birds and hair of mammals are not as liable to be attacked by moths as when the skin is preserved with arsenic. This preservative when properly applied abstracts the oil from greasy skins, thus preventing them from becoming decayed through carbonization, as nearly always occurs in ducks’ skins after a few years. It is a deodorizer, all disagreeable smells leaving the skin to which it is applied; and above all it is not a poison. I used this dermal preservative, as we have named it, as an absorbent while skinning birds, especially small ones, as then the plumage is dusted with it necessarily, which insures more or less protection to the feathers from the attacks of moths.
To render my preservative, or indeed any other, effective, it must be thoroughly applied to the skin; all the portions, especially those to which any flesh adheres, must be well covered with it, and the fibre of the muscles should be broken up as much as possible. But a small portion, at best, of arsenic is soluble in either water or alcohol, and but a little in the juices of the skin, whereas in my dermal preservative at least three-fourths of that which comes in contact with a moist skin is absorbed, thus thoroughly preserving the specimen. In the case of a greasy skin, remove as much fat as possible by peeling it off or gently scraping until all the little cells which contain the oil are broken up and the skin appears; then coat the skin liberally with the preservative, when it will be found to absorb the oil. Allow this layer to remain a few minutes, then scrape it all off and coat again with a fresh supply. Continue to do this until all the oil that will flow out is absorbed, and then dust with a final coating.
There are two chemical processes carried on in preserving oily skins, one of which converts the oil into soap, and this is in turn absorbed and dried. Thus the preservative which has been scraped from the skin can be after a time used again, as it has lost but a small portion of its efficiency. It might be borne in mind, however, that all the fat cells possible must be broken up, as the skin which surrounds these is, in a measure, impervious to the preservative, which must, in order to absorb oil, come in contact with it.
Section V.: Other Methods of Preserving Skins.—Skins may be temporarily preserved by simply using black pepper, but the effect is not lasting. The same is true of tannic acid, but either of these, alum, or even common salt, will do as a substitute for the preservative until the skins can be got into the hands of a taxidermist, or until the collector can procure the proper preservative. I will here mention that the dermal preservative costs only twenty-five cents per single pound, and this quantity will preserve at least three times as many skins as the same amount of arsenic.
A good method by which large skins may be temporarily preserved is by salting them. Simply coat the inside of the skin with fine salt, turn it, smooth the feathers and fold the wings neatly, then pack in paper. The salt prevents the skin from quite drying, and thus it can be moistened much more readily, and made into a skin or mounted. The advantage of packing large birds in so small a capacity is obvious to any one. Two collectors whom we have had out the past season have sent in some thousand large skins in this condition; and these we shall endeavor to work up within six months’ time, as salted skins become quite brittle if allowed to lie too long. They should be kept in a dry place, as salt absorbs moisture, which causes the skin to decay. They are also liable after the first year to be attacked by dermestes and anthrenus.
Birds which are in a bad condition through having been dead a long time may be sometimes skinned, in case of rare specimens, by using great care. Sprinkle the inside of the skin well with preservative, as this tends to set the feathers, being a stringent, keeping the skin as straight as possible, as folding it is liable to loosen the feathers. The intestines of birds may be removed and the cavity salted when large birds are to be sent from a distance.
