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Re: flapping from gliding



At 11:08 AM 9/25/96 -0500, Bonnie Blackwell writes:

>Say you have a glider who evolves in a forest with lots of trees (as most
>seem to do).  When you glide you have no worries about getting to another
>tree - as long as the tree density remains stable.  Let's say that
>environmental change (drying, increasing seasonality, temperature change
>or even new species that use fire for germination like the Eucalypts
>leading to more fires) causes a decrease in tree density.  If you want
>to continue to glide, you better increase your accuracy if you want to
>be sure to land in a tree rather than becoming a messy schplatt on the ground.

Or perhaps they didn't need a reduction in trees to fly.  What if
flapping evolved as a mechanism to *avoid* trees?  If the protobirds
are gliding in a dense forest, there would be a selection pressure for
increased manuverability, so the animal wouldn't pull a "George of the
Jungle" routine.  As the wings develop to allow greater
manuverability, they become stronger over time.  This allows for
greater and greater flapping power, until sustained powered flight
becomes feasable.

Rob Meyerson
Orphan Vertebrate Paleontologist

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