Re: Feathers vs Wingspan

["James R. Cunningham" <jrccea@bellsouth.net>]

philidor11@snet.net wrote:

> If I understand you correctly.........., there's a limit
> to how big a bird with a lot of feathers can be.

No.  There may be a limit to how big a bird with a lot (or a little) of
feathers can be and still launch and fly.

> Assume that there is an ecological niche available for big flyers
> and that many heavy feathers are not required for a very large
> animal to fly; the pterosaurs appear to demonstrate these assertions.

I'm sorry, I don't follow the line of reasoning.  Are you saying that if
we were to pluck most or all the feathers from say, an albatross -- then
it would be able to fly better?  Moulting birds demonstrate that as wing
area is reduced, body weight is usually also reduced correspondingly in
order to maintain a relatively constant wingloading, but that there is a
consequent drop in flight efficiency.

>  Naive question:  wouldn't a bird with fewer feathers be able
> to increase its size, particularly wingspan successfully and
> so move into an available niche?

Yes, it can become larger, change its life style, and move into a
terrestrial niche.  As it gets larger, it will reach a point where it
cannot launch without an external assist, and that point seems likely to
occur at lower weights in birds than in pterosaurs, partly because of a
probable difference in launch technique.  For example, it appears to me
that Qn could probably still do a ground launch satisfactorily in today's
atmosphere during a dead calm. It appears to me that Argentavis probably
couldn't.

>  Are there other adaptations in all birds that would prevent them from
> relying less on feathers
> as a strategy?

I don't know.  I don't mess much with birds.  I have some trouble
imagining them going bald and then developing a flight membrane with
appropriate internal structure, all while maintaining flight ability
during the interim generations.