The objective of the person who is carrying out a postmortemexamination
should be to observe and to record. There are inherent dangers in attempting to
interpret findings at an early stage or as the postmortemprogresses. Something
that may appear to be significant initially, such as damage to a pectoral muscle or
a pale liver, may subsequently prove to be of little consequence because, for
instance, bacteriological examination (the results of which may not be received
for 3–4 days) reveals that the bird died of an overwhelming infection. It is there-
fore best to reserve judgment until all tests are complete. Too many investigations
of avian mortality in the past have been hamstrung by premature judgements,
based on inadequate information, regarding the likely cause of morbidity or
mortality.
The assessment of “condition” has for long been controversial and yet is con-
sidered an important index in studies of survival and reproductive success
(Bowler 1994; Fox et al. 1992; Moser and Rusch 1988). Those examining birds
post mortemare usually anxious to give a “condition score” because this is part of
evaluation and provide some indication as to the likely cause of death. Methods
of assessing condition include:
- Relating bodyweight (mass) to standard morphometrics—an important
reason for measuring, as well as weighing, birds post mortem(but it must be
remembered that carcasses suffer from gradual evaporation, and hence
weight loss). - Assessing and scoring the amount of fat, both subcutaneous and internal.
- Measuring muscle (especially pectoral) size, both macroscopically and
histologically. - Whole body measurements, for example, the TOBEC system (Samour
2000).
Each of these methods—and, indeed, others—has its own devotees and which,
if any, is used will depend upon the protocol being followed. However, it is most
important that some assessment is made that might aid others in relating find-
ings from one bird to another. Thus, measurements of carpus, tarsus, etc. should
be routine, as well as bodyweight calculations, and there should be some scoring
system for as many as possible of the other parameters, such as the quantity of fat
that is visible or the size of pectoral muscles (for further discussion of body con-
dition assessment, see Chapter 4).
Space does not permit detailed discussion of all body systems, but mention
should be made of the reproductive tract because of the importance in ornitho-
logical studies of assessing and measuring breeding success (Newton 1998).
Close examination of the reproductive system is therefore often useful. Sexing
192 |Information from dead and dying birds