> north and white-backs to the south). Over the last several years I
> have
> noticed an increase in the number of White-backs (and mixed birds) in
> Canberra and to the north of the city. This change has been noted by
> many others as well. So in this area it appears White-backs are moving
> north.
>
Perhaps it's a bit like the Black-eared/Yellow-throated Miner thing, but
on a massive scale. Changes in land use might well have brought the
white-backed and black-backed Australian Magpies into a broader edge of
contact than was previously the case. The Great Dividing Range &
subsidiary ranges, which were previously some kind of barrier between
the two in most places, are now substantially cleared, with prime Magpie
real estate now being one of the main habitats. Ipso facto, the zone of
introgressive hybridisation between the two forms is now visibly broader
& still growing. Maybe in a few more hundred or thousand magpie
generations, the two forms will again merge, at least in the South
East!!??
Lawrie Conole
Geelong, Victoria, Australia
http://www.vicnet.net.au/~raou/painted.html
http://www.xnet.com/~ugeiser/Birds/TripReports/JavaBali96.html
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