in such cases is, usually, what led to the starvation? Often the answer to the latter
is complex. Thus, initial investigation of a group of waders found dead on the sea
coast may reveal that the proximate cause of death was emaciation and hypother-
mia, but more detailed investigation may indicate that the underlying factors
leading to that state of affairs include large numbers of parasites in the intestine,
renal (kidney) disease, and exposure to unusually severe weather. An alternative
scenario is that a bird is found to be heavily infested with internal parasites but this
is because it has had to change its diet—perhaps because of climatic change or
paucity of the usual prey species—and as a result has acquired the parasites from
a novel food item. Here the parasites have caused death but they were secondary
to other factors. In such cases, all available information needs to be obtained from
the carcasses and must then be put together with relevant background history in
order to build up a picture. Understanding the death of wild birds often resembles
a jig-saw puzzle; no one piece provides the full answer, and the puzzle is only com-
plete when all the portions have been put together.
Whether one is involved in diagnostic pathology or postmortemhealth moni-
toring, the ability to examine a dead bird correctly, in a systematic and repro-
ducible way, to describe what is found and then to take and submit specimens, is
of the utmost importance. This point is reiterated later. Dead birds can be of any
age. Nestlings and fledglings present various challenges. The investigation of eggs
and embryos needs particular skill and experience. In this chapter all these proce-
dures, together with the collection and storage of samples, will be discussed.
There are many sources of dead and dying birds. Sometimes individuals are
submitted by concerned members of the public. On other occasions, the mor-
bidity or mortality rate is so high that a concerted effort is made to collect speci-
mens for examination. From time to time researches request carcasses for specific
studies—for instance, to search for viruses such as that which causes West Nile
disease, or to investigate causes of death and pathology of a particular species
(Cooper 1993a). Live birds are sometimes taken into wildlife rehabilitation cen-
ters and these too can provide useful information if subjected to systematic
examination and appropriate sample-taking (Cooper 2003a).
Clearly, in such cases, there is often bias in sampling. As a general rule, mem-
bers of the public are more inclined to report dying or dead birds of a popular or
rare species than pests, but it is always important to obtain as much background
information as possible. There is merit in visiting the site oneself and collecting
bodies or samples rather than relying on material that is sent in. The presence of
live birds, even if they are moribund, may permit the taking of blood and other
antemortemsamples and this, coupled with full necropsy and other laboratory
investigations, can provide much valuable information (see Tables 8.4 and 8.5).
180 |Information from dead and dying birds