Roger,
That seems like you have assumed that over the millions of years, they
have not previously dispersed to those two isolated islands. If they
have done it now they surely have done it before and presumably not
established themselves. And surely several rails have done exactly that
before in other locations and evolved into new species. Maybe the
difference is their survival there now and that may be aided by human
settlement.
Philip
-----Original Message-----
From:
On Behalf Of Roger Giller
Sent: Friday, 15 May 2009 11:35 PM
To: Birding-Aus
Subject: Purple Swamphen in Birdata
I noticed the current "Bird of the Week" in Birdata is the Purple
Swamphen.
The following caught my attention:-
Though most Purple Swamphens are sedentary, readily remaining at their
chosen wetlands, a few are far more adventurous. This wanderlust has
been illustrated by the establishment of populations of Swamphens on
both Lord Howe and Norfolk Islands in the late 19th century. These birds
originated from populations in eastern Australia or, perhaps, New
Zealand, so this must have entailed flying vast distances over the open
ocean -- no mean feat for such an ungainly flier.
Does this mean that after being quite happy to stay in Australia and/or
NZ for millions of years they suddenly decided to migrate to two
isolated islands about 100 years after Europeans "settled" them.
Surely it is far more likely that human intervention played some part in
their arrival.
Roger.
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