a bird should not be difficult but sometimes, especially if the bird is immature, if
there is postmortemchange, or if it is a non-breeder, the gonads may be difficult
to see. The use of a handlens and strong reflected light can help but if this fails, a
portion of the relevant tissue can be taken for sex determination by histological
examination (the section often also contains adrenal gland, which can sometimes
provide information about stress and endocrine function).
During necropsy, always note the appearance of the ovary or testes. In species
such as falconiforms, the presence or absence of a vestigial right ovary should also
be recorded. Whenever possible—and always when a series of birds is being
examined—the size of the gonad(s) should be noted, by measuring, weighing, or
scoring. The state of activity of the ovary (follicle development) is also important.
The color of the testes should also be recorded: sometimes they are pigmented.
Other observations on the reproductive tract can provide useful information.
Readily visible, well developed, oviducts usually indicate that a bird has laid eggs.
For many species reliable data are lacking so again the size of the organ should be
recorded by measuring, weighing or giving it a score.
Gross examination of the reproductive system can always be supplemented by
histological examination. The gonad and tract, or parts of them, should be fixed
in buffered formalin 10% and hematoxylin and eosin—stained sections pre-
pared. Where there is particular interest in breeding history, reproductive organs
can, after measuring and weighing, be fixed in formalin for study at a later date.
Weighing of organs—especially liver, heart, spleen, kidney, and brain is to be
encouraged whenever possible. Organ : bodyweight ratio change can be a feature
of some infectious and noninfectious (especially toxic) diseases.
A gross postmortemexamination does not per seprovide the answer to the bird’s
death or its failure to thrive, and the answer (the final pieces of the jig-saw, as
described earlier) is the carrying out of laboratory tests, such as toxicology and
bacteriology. The taking of samples is discussed in the next section.
The retention of material following postmortemexamination is an important
part of any investigation for several reasons:
- It may be necessary to go back to the carcass in order to carry out additional
investigations. This can happen, for example, if laboratory tests indicate
that a bacteriological infection is involved, in which case samples taken can
be cultured in order to identify those bacteria. - Carcasses or other material may be required for legal purposes—if, for
example, a court action is to be bought in connection with the bird’s death. - Material may be needed for research purposes. The requirements can range
from whole bodies, study skins, or skeletons for museums, to the retention
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