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Re: Science feather strength debate
On 11/1/2010 8:28 PM, Erik Boehm wrote:
I don't see the lack of a powered upstroke as a convincing argument against
some form of flapping behavior (I can see it as an argument about the upper
limits to what sort of power it could get by flapping)
I agree. In a gliding-to-ridge-soaring-to-flapping flight transition
scenario the up and down strokes capabilities would not need (or even be
likely) to evolve simultaneously. Logically, the downstroke would come
first, evolving from weight-support, braking and control needs, even in
scenarios that skip the ridge-soaring phase.
The notion that purely passive gliders made a gradual transition to
flapping flight in micro-environments wherein there was a daily or even
seasonal enabling airflow over a fortuitous substrate, such as in some
coastal environments, is a very appealing one, btw.
What I especially like about it -- such environments tend to be narrow
interfaces w/ very different but resource-rich areas on either 'side' --
e.g., forest vs marine.
Any perching or ridge-soaring predator/scavenger glider in such an area
would daily encounter transitional air on the 'edges' where the airflow
ranged from not-so-enabling to downright unfriendly, making even minimal
flapping ability a big advantage over prey, predators and direct
competitors when attempting to seize the various opportunities such
areas would provide.
Does anyone know the history of it in the literature?