The Technique of Preparing Bird Skeletons for Study by Maceration

The Technique of PreparingBird Skeletons for Study by Maceration

* J. Hill Hamon, Indiana State College, Terre Haute, Indiana

The preparation of bird skeletons by allowing the flesh to rot or be picked off is described in this article. The author is Associate Professor of Zoology at Indiana State College.

Bird skeletons are very expensive. The cost picked nearly clean by these small sapropha- of an articulated skeleton of a common chicken geous insects. Skeletons prepared by this

can run as high as $55.00 if purchased at method, however, are greasy, and some ob- Downloaded from http://online.ucpress.edu/abt/article-pdf/26/6/428/20549/4440716.pdf by guest on 29 September 2021 a biological supply house. Some articulated jectionable connective tissues remain on the skeletons of pigeons cost as much as $40.00, bones. while disarticulated skeletons, with loose bones Avian skeletons can also be prepared for contained in a small box, generally run over study by macerating techniques. Maceration $13.00. If you "do it yourself," however, is the process of rotting away tissues from good skeletal preparations can be made at skeletons placed in water, by bacterial action. little or no expense. This technique has been used for centuries in There are several methods of preparing the the recovery of skeletons for use in osteolog- skeletons of birds for study. The carcasses ical studies. Eustachia, a professor at the can be buried in soil, and their skeletons later Papal School of Medicine in Rome during the reclaimed after all the soft body parts have sixteenth century, was well known for his decayed. This technique is risky because of use of maceration in the preparation of hu- the possibility of losing some of the smaller man skeletons for study. bones. Another commonly used method in- There are several advantages of the use of volves boiling the bird in water until all the maceration over other techniques in the re- flesh can be pulled off so that the skeleton can covery of bird skeletons. When the macerating be recovered. This is a rather poor method because boiling softens the bones and causes severe damage to them. Other workers prefer to "bug" birds in order to acquire their skeletons. The birds are skinned, eviscerated, dried thoroughly, and then placed in a special col- ony of dermestid beetles. The bones are

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Fig. 1. Care should be taken not to pull off the pygostyle when pulling out the tail feathers.

428 THETECHNIQUE OF PREPARINGBIRD SKELETONS 429

the skeleton are removed. Special care should be exercised not to cut into any bone. The animal is then eviscerated and sexed. If the specimen is to be used for research purposes, the sclerotic bones surrounding the eye should be saved, as well as the trachea and hyoid apparatus. These are usually dried separately and not macerated. The bird is then placed in a large clean bottle and covered completely with ordinary tap water. A tight-fitting lid is then fitted

on the bottle. A label can be tucked under Downloaded from http://online.ucpress.edu/abt/article-pdf/26/6/428/20549/4440716.pdf by guest on 29 September 2021 the edge of the lid upon which all pertinent data on the species, locality of collection, collector, date, and sex, is recorded with water proof ink or indelible pencil. "Pouring-off" is a very important part of the skeletonizing process. The water covering the specimen should be poured off daily. This water will usually be discolored, and will have an unpleasant odor because it contains many small fragments of the decaying soft parts. "Pouring-off" should be done with care so that small bones are not dumped down the Fig. 3. The "roughing-out" should be done with care so drain. The specimen is then flushed with sev- that bones are not broken. Most of the muscles are cut away. eral changes of fresh water and inundated again for another day. The preparation should not be allowed to stand for long periods be- process has been completed, the bones are tween "pouring-off" times. Usually, if this completely clean. There is no trace of resid- ual fat, and there is no disagreeable odor. No connective tissues remain on the bones to obscure osteological characters as they do in most of the other methods of preparation. There are disadvantages for some in macerating. The skeletons, when recovered, are usually completely disarticulated. If an articulated skeleton is required, this method is not usually desirable. It also generally takes longer to prepare a bird skeleton for study by maceration than with some other recovery methods. The odors associated with the decay of the soft parts during the early stages of maceration are often offensive. It is easy to prepare a bird for skeletoniza- tion by maceration. First, the bird is skinned. It is recommended that the wing and tail feathers be plucked out individually so that the bones will not be broken. Care should be taken not to pull off the pygostyle, a bone formed by the fusion of several caudal verte- brae, when removing the tail feathers. Next, the carcass is "roughed out." All muscles and Fig. 4. The carcass is dropped into a bottle of ordinary connective tissues that can be cut away from tap water. 430 THEAMERICAN BIOLOGY TEACHER happens, molds form on top of the water, and should they come in contact with the bones, the bones are often discolored and actually destroyed. If the lid of the bottle is replaced tightly between times for "pouring-off" there will be very little odor detectable near the macerating specimen. The time required for a skeleton to be completely cleaned by bacterial action in water varies considerably with temperature, the con- dition of the bird carcass before maceration, the type of water used to cover the animal, Downloaded from http://online.ucpress.edu/abt/article-pdf/26/6/428/20549/4440716.pdf by guest on 29 September 2021 and probably many other factors yet unrecog- nized. I have seen skeletons cleaned completely in less than a week in Florida in summer, yet I have macerated some birds for almost two months in summer in Indiana before they were skeletonized. The decay bacteria appear to be more active at higher -~~~~~ temperatures. Birds that have been frozen before skeletonizing appear to decay more slowly than do freshly killed specimens. It is difficult to macerate birds in water with high sulfur content, even in areas of higher tem- Fig. 6. The "pouring-off" should be done in running water. peratures. Ordinary city tap water seems to Do this slowly because small bones can be easily lost work as well as distilled water for macerating down the drain. purposes. After maceration is completed, the cleaned boxes are usually used to contain skeletons of bird skeleton must be stored properly. Small birds that are prepared for osteological research or for teaching collections. A reference number should be inscribed on each individual bone in water-proof ink and a catalog of reference numbers should be maintained. This numbering protects against inadvertent mixing of bones of different skeletons that might be in use at the same time. A bird skeleton can be articulated so that it may be used for display purposes. It is a fairly difficult task to successfully articulate a bird skeleton at the first attempt. Articulating can be done well, however, if quick setting contact epoxy cement is used to weld the bones together. Thin wire is also useful in strengthening the wings and for holding the preparation in the desired position. A prepared articulated skeleton of a bird is useful for reference when you first perform an articulation. Good articulations, however, can be accomplished by using a good drawing or photograph of such a prepared specimen as a reference. Drawings may be obtained from biological supply houses, while pictures of articulated skeletons of birds can be found in Fig. 5. Pertinent data can be written an a label with an indelible pencil, and inserted under the bottle lid. most zoology texts. THE TECHNIQUEOF PREPARINGBIRD SKELETONS 431

eontologists for comparative purposes in the identification of fossil bird bones. The maceration of vertebrates other than birds for skeletons perhaps offers some workers more disadvantages than advantages. Mammal bones have epiphyses that are usually loosened and lost from the ends of long bones. It is also difficult to macerate mammal skulls without having all the teeth fall out. These teeth must be cemented in place early in the

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: What birds are best to macerate for a ...... :...: : tS l; t : S :t::tiE 0 t0 t ...... s teaching collection or for articulation? Birds that are not protected under state or federal laws must be used. Examples of these are : : :fi i : :0*s* ;4!0X: SaiEAi;;;;;.f;iSC00009;;;00:f000ft00td;ff:fFi...... -.a.::: ...... 0; crows, pigeons, and chickens. The bones of ; : W0 0 000 0 000 ; ; ; t ;ta.....;-t00:t:;:00:-.;0.00-000tl0...... stAitidEX0.a...... these animals are large enough so that they may be studied without the aid of binocular : 0 : S :0 : XE; ::: f ....,.0,.Sig:.:.000j;ftES;00000C',...,.;.,,.'.',Sl040000:00.;0:S'...... microscopes, and being larger and sturdier, f:0; i; At \,.,...,...... 0i; :0 ,l;!E,...i;..,,,,.,-.-,.X :' .-!,,-''illTES:'t;.:f; ti;: ;:C?.:Xt . :0..-:...... l

are much easier to articulate than the smaller, : :: i: :} s . . j i :: i i.~~~~~~~..>..h#.>...... >...... _~~~~~~~~~~~~~~~~7V...... :: more delicate bones of smaller birds. You Fig.8. Onlymoture birds should be macerated.Th....p...o... must a state and federal scientific col- thetibiotarsusone on on the right is froman immature bird,while~~~~~~~~...... acquire thatthe immature theleft boneis from is rounded,a maturespongy,specimen.Notice~~~~~~~~~~~~~~~.... andlacks~~~~~~~~~~~~~~...... lecting permit if you plan to build a skeleton the finer osteological detoils~~~~~~~~~~~...... b n ...... collection of most other species of birds for research purposes or for a teaching collection. Only adult birds should be used in skeleton preparation by maceration. If immature forms are used, ossification of the ends of the bones will not be completed, and they will be rounded, spongy, and almost useless for study. There are several uses for avian skeletons. Science Education (1963-2000) They are very useful in illustrating and com- The College of Education of the University paring skeletal homologies with other classes of Toledo has issued Educational Comment, of vertebrates. The special skeletal adapta- Spring, 1964. It is edited by Robert R. Buell tions necessary for flight can be easily demon- of the College of Education, and the issue strated by the display of skeletons or individual may be obtained by writing the Editor. It bones. Skeletons are of the greatest value for consists of essays by Ellsworth Obourn, Wil- use in osteological and myological research. lard Jacobson, Alma Wittlin, T. R. Porter, They are also used extensively by avian pal- George Mallinson, and Robert R. Buell.