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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?