There are of course a range of possibilities(e.g. mutation) for the colours in
parrots hower feather abnormalities in psittacines are often associated
Circoviral Disease. This is an endemic (but unfortunately due the bird trade
now worldwide) virus which infects young parrots.
Clinical presentation is the characteristic break down of the keratin
structures (beak and feathers - hence its other name) leading to a dirty
appearance in the Cacatuidae (e.g. cockatoos and galahs) and feather colour and
shape distortions in the Psittadae. In King Parrots (Alisterus scapularis)
there is often a reversal of the colour. So where yellow should be on the
underwing it appears above. This is largely an artefact of the distortion in
the feather rachis rather than actually reversal. In other words the distorted
feather shaft is twisted. In Lorikeets the disease presents as failed primary
feathers and retricies hence the common name "runners".
The disease is immunosuppressive and these birds usually contract a secondary
infection. This may come about because the beak distortions make it difficult
to forage properly and the birds depend on poor food sources (low proteins and
hence poor plumage) and feeding tables. The latter act as little disease
transfer stations as the infected young birds drop infected powder down and
faeces into the food consumed by healthy birds. This is only one disease that
can be passed around through feeding tables.
The disease largely effects the young and is harboured by timber (tree hollows
become infected) for long periods. WIRES received hundreds of parrots infected
with cricovirus every year and these birds are quarantined and euthanased as
soon a possible. The disease is cover by a federal management plan
Chris Lloyd
Training Officer
WIRES
PO Box 260
Forestville NSW 2087
==============================www.birding-aus.org
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