Philip Maher obviously knows his birds and it'd good if contributed more
often here, but he has hit one of my peeves.
I reckon linking a bustard turning up near Deniliquin to drought is what
psycologists call confirmation bias. It is quite a reasonable belief
that rainfall patterns influence inland bird movements - the problem is
then interpreting everything in light of this belief.
However take a look at the rainfall maps 1890-present linked here:
http://www.longpaddock.qld.gov.au/Products/AustraliasVariableClimate/
With a little imagination for most years you can construct an explanation
for a bustard appearing in the Riverina. If there is good rain over the
(current) bustard range of northern and western Australia you can say
its an irruption due to successful breeding. If there is poor rainfall in
northern/western Australia you can say they have been forced to move due
to lack of food. If there is above average rain in the Riverina you can
say increased food supply has brought them, if there is drought in the
Riverina ...
So a bustard can turn up pretty much anytime in Deniliquin and it can
be attributed to rainfall patterns - making such inferences, at least
from scientific viewpoint, completely useless.
You can also contive a just-so explanation based on rainfall for
Painted Finches appearing in Jerilderie, but however plausible such
post-hoc explanations sound I don't think they are informative.
Observations of long distance dispersal by Painted Finches certainly are
informative - incidentally there is an older record from Katherine
Gorge which is about 100km as the finch flies from Gunlom. But you
still have to consider competing explanations. There are thousands of
pairs of Painted Finches in cages closer to Jerilderie than any of the
other sightings mentioned. I still think this makes escape/release
a more likely explanation but everyone else seems to disagree so I'm
probably wrong.
Andrew
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