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Re: Flight again (was Re: The Lizard of Oz)



David Marjanovic wrote:

> > asymmetrical feathers are not required for lift production.
However, the
> cost
> > of the moult is cheaper if the lifting feathers are asymmetrical
because
> the
> > asymmetry allows use of a less massive shaft.  Is it possible that
moult
> > expenses are related to development of asymmetry in flight feathers?

>
> Given that all flightless birds moult... don't they?

Don't know.  But I strongly suspect that feathers came before flight, so
don't
see that in modern flightless birds it's relevant to the issue except
that it
would lead one to believe that birds may have been moulting before they
developed flight, and that therefore moult expenses may be related to
the
development of asymmetry in flight feathers as I speculated before.  If
you are
flying and moulting, then modifying the feather so that it is
asymmetrical is
going to allow you to reduce the mass in the feather shaft, and thereby
reduce
the biological expense of the moult (extra food is required to produce
the more
massive feather shaft required for flight with a symmetrical feather).
Which
was my original point in my first post.

Jim

> > David Marjanovic and someone else [HP Tim Williams] wrote:
> >
> > > > This design
> > > > pre-adapted the symmetrical vaned feathers for lift.  The wing
> feathers
> > > > then
> > > > became asymmetrical.  Evolution of flight by successive
exaptations.
> > >
> > > Of course by successive exaptations!