On Fri, May 15, 2009 at 11:35:10PM +1000, Roger Giller wrote:
> 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.
The Birdata blurb is a littled understated - Swamphens (Porphyrio) are
notable island colonizers. Their Pacific populations have suffered ove
the last few thousand years as humans have also colonized these island -
some are still being discovered from sub-fossil remains others may have
perished completely unknown. Swamphens were in Lord Howe Island when
humans arrived - but the endemic White Gallinule didn't survive long.
I don't know if there is evidence of past Porphryio populations on
Norfolk. Genetic evidence is being interpreted as the Pukeko stemming
from 2 separate immigrations into NZ, the South Island Takahe from a
third older immigration, and the extinct North Island Takahe could even
be from a 4th.
Andrew
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