forceps are ideal for grasping tissues during dissection but can damage samples
destined for the histology laboratory. A handlens or dissecting loupe is invaluable
for the investigation of small birds or tiny lesions.
The examination of young, “neonatal,” birds is not always straightforward.
They are not just small or immature versions of the adult. The immune system is
only just starting to develop and to respond to antigens in the environment.
Powers of thermoregulation are usually poorly developed, especially in nidi-
colous species. Therefore, susceptibility to certain infectious agents, as well as to
physical factors such as cold, may be enhanced. The person carrying out the
examination must be aware of these differences from the outset, and investiga-
tion of the young bird should follow standard techniques for “neonates,” similar
to those originally developed for domestic poultry and now widely extended to
psittacine and raptorial birds (Cooper 2002). An important feature of the
necropsy of young birds is the examination, measuring, and sampling of the
bursa of Fabricius: this organ, which lies adjacent to the cloaca, is a key part of
the immune system and its investigation is vital if mortality and morbidity in
young birds is to be fully investigated. The bursa and also the thymus should be
examined, measured, and fixed in formalin for subsequent examination. If in
doubt over the examination of young birds, the advice of an experienced avian
pathologist should be sought—and this approach applies also to the investiga-
tion of eggs and embryos (see below).
The comprehensive examination of eggs is a highly specialized field. Much
information has been gained over the past few decades from studies on the
domestic fowl and other galliform birds, but also from other captive birds,
including passerines, parrots, raptors, and owls (Cooper 2002, 2003b). The
examination of eggs of wild birds often does not follow a standard protocol, and
toxicologists tend to take samples in a different way from those who are interested
in infectious disease, developmental abnormalities, or incubation failures. Space
does not permit a detailed description of the specific techniques that should be
followed in order to obtain maximum information from eggs and embryos, but
a protocol is given (Appendix II), together with a specimen report form
(Appendix III).
Measuring eggshell thickness is an important part of assessing eggs, whether
or not they are fertile. Various methods can be employed; a useful index was
described by Ratcliffe (1967) and this and other methods were explored and
compared by Green (2000).
Key features of any postmortemexamination are (a) the recording of all that
is seen or done, (b) the taking of samples, and (c) the retention of material for
subsequent study.
Postmortemexaminations (necropsies)| 191