On Wed, 6 Jun 2001, Ralph REID wrote:
> One report says that the longest study yet conducted was by physician
> Charles Kemper over a 38-year period, beginning in 1957. In that period he
> collected 121,560 birds representing 123 species. ...
This occurred at a 300m TV transmitter tower. This is about the same
height as the Centrepoint Tower in Sydney. When vertical the blade on
a large wind-turbine might reach to roughly 100m. The guy wires and
lights of US communications towers are thought to be a key part of
massive overnight kills - essentially under overcast conditions
the lights attract birds which collide with guy wires. Wind turbines ,
which don't have guy wires or lights aren't going to kill birds this way.
Long distance nocturnal migrants, in other parts of the world, under most
circumstance tend to fly above 100m which hopefully means mid-journey
collisions with wind turbines are not likely. Collisions by "local"
birds making shorter movements either diurnal or nocturnal, is another
matter. Collision with wind turbines will surely kill birds - just
as collisions with other structures - power lines, fence, houses do.
It is one matter if common local birds, perhaps Nankeen Kestrels and
Black-shouldered Kites are killed in small numbers, it is much more
serious matter if a rare or threatened species is killed and its hard
to pick a worse species to have at risk than Orange-breasted Parrots.
Wy personal opionion is that in many locations the environmental impact
of wind turbines is acceptable - although we can certainly reduce it -
but some locations shouldn't be used.
As to the risk to birds of Australian communications towers, I believe
Sydney's TV transmitter towers are in the range 100-200m high. This seems
to be smaller than the US towers that produce major kills. Of course
there are other communications towers around Sydney.
My impression that typically along the NSW coast TV transmitter towers
are under 100m high but situated on the tops of ranges, hills etc.
Its conceivable that birds making nocturnal movements north<->south could
navigate along ranges greatly increasing the likelihood of collisions
Even if Australian communication towers don't present a significant threat
- and presumably they don't or we'd know about it - kills in collisions
might provide interesting data on bird movements - effectively sampling
the movements.
Andrew Taylor
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
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