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Re: The life of birds



Tony Thulborn wrote:

> My understanding of the program was somewhat different.  Attenborough
> identified absence of predators (esp. in New Zealand) as reason for the LOSS
> of flight, but didn't mention PRESENCE of predators as reason for the ORIGIN
> of flight.  He didn't offer any "good argument" at all for the development
> of flight. Instead he stuck, in very orthodox fashion, to tired old
> scenarios of "ground up" versus "trees down" (or "cliffs down").  The
> pictures were fabulous, but the narrative was ultra-conservative - despite
> usual enthusiasm of the narrator!.

I watched it again yesterday, and he definitely took the predator
avoiding angle. He said that because flight was so expensive to
maintain there has to be an impetus for its development and
continued use. He used the example of the frilled dragon, and how
if it does not scare off a predator with the extended frill it will
then race of on its hind legs to make itself bigger. Mr Attenborough
then suggested that if the display mechanism was on the wings,
followed by the same sort of running display, that the ground-up
scenario may have happened. He also used the flying lizard (of Borneo?)
as another example, of how flight may have developed trees down (or
up).

He also showed many pieces of footage with birds taking to the air
suddenly to avoid predation (geese escaping Arctic foxes, flamingos
scared up by a jackal, and so on) to show how the birds in question,
if flightless and out in the open, would have been "sitting ducks"
(and I believe he actually uses that term). Hence the title of
the first episode "To fly or not to fly".

Therefore he actually mentions various flight/feather origin scenarios.
Ground up, trees down, wings as display mechanisms, escaping predation,
even feathers as dynamic insulation (raising feathers to cool off,
lowering them to keep warm). In other words a nice balanced (and 
non-commital) narrative.


-- 
____________________________________________________
        Dann Pigdon
        GIS Archaeologist
        Melbourne, Australia

        Australian Dinosaurs:
        http://www.geocities.com/capecanaveral/4459/
        http://www.alphalink.com.au/~dannj
____________________________________________________