The former ranges of present day bird species may indeed have been very
different from their present day ranges. Birds, and other kinds of living
things, are a lot more adaptable than we think?we only observe them for a
fraction of their species 'life-span'. Moreover, although specific
adaptations are important, in the aftermath of major climatic or other
environmental uphevals, which species occupy which niches and expand into
which areas is probably largely a matter of chance, which species get lucky
in the first few generations.
I was reading a book about the Riversleigh deposits recently (which is in
the Gulf Country, Gregory River NP) and the fossils of Australian fauna they
contain. About 100,000 years ago, this would be before the drying out
associated with the 'last' Northern Hemisphere Ice Age, the Rioversleigh
area was tropical grassland with rainforest along the rivers (perhaps a bit
like parts of Kakadu today), ie a lot wetter than presently. The most common
parrot at the time, according to the (sub-)fossil record was a species of
cockatoo indistinguishable in its skeletal details from the contemporary
Long-billed Corella. There is no reason to think that it was not the
present-day species, but look at the present range of this species, and the
habitat that we have known it to inhabit!
Also on the theme of Galah and other other urban parrots. One of the
earliest people to write about Canberra and its birds was the schoolmaster
at the Duntroon settlement in the 1850s. In the course of ten years of notes
he only refers to Galahs once, as a rarity!
John Leonard
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