On Mon, Jan 22, 2007 at 06:37:30PM +1100, Dave Torr wrote:
> Whilst the figure for cell phone tower deaths of 4-50 million (a huge
> range!) in the US is alarming,
This sound like an estimate for bird deaths from *communications*
towers in the USA. These can be very tall structures, 100+m high,
often for transmitting radio and/or TV. See http://www.towerkill.com/
for a pile of info about the circumstances thought to cause deaths.
Mobile phone base stations, at least around here, are not tall structures.
They seem mostly placed on existing building and stand less than 5 metres
above it. There are often taller nearby structures and the mobile phone
base stations don't look to add much to the collision risk at least in
the cluttered urban environment. You do see smaller towers (10-20?m
high) purpose built for mobile phone base stations and what look like
base stations located part way up radio/TV towers.
Radio/TV transmitters are much less numerous - they cover a larger area
- but are much more imposing structure. A 20-100+m high tower built on
the highest terrain available - so the top can be several hundred metres
above nearby terrain. I do a bit of mountain running south of Sydney
and there are radio/tv transmitters on a number of high points (Broker's
Nose, Mount Kembla, Knights Hill, ...). A migrating bird following the
eastern edge of the dividing range would pass close to these -
but I don't know if any bird do navigate this way.
Andrew
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