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Re: Science feather strength debate



Greg,

You just called me unscientific. Yet you used these terms: "duh, -- hello
-- can't some of you read?" You do have a point: when I read your posts
sometimes I wish I could not read.

Please, for all the readers of the DML, define the scientific process as
you understand it. And, while doing so, please explain why no one in the
world can reproduce your results, and why no authors are allowed by their
editors to cite your work in peer - reviewed literature.

Also, did you mean to use the word pessimism? Because, surely, the truth
is to be found in the data, not in your hopes of what the data will show.
A little bird called "Avisaurus" told me that.

-Jason

> Oh this is just unbelievable.
>
> In a message dated 11/4/10 9:54:54 AM, jaseb@amnh.org writes:
>
> << >>> a 20% difference in mass makes a big difference in aerodynamics and
>>> This is ridiculous. The mass of an individual bird can vary by 20% or
> more
>>> over a matter of hours (if it gorges) or days (as body fat deposits
> vary).
>>> It is common for very long distance migrating birds to start out heavy
> with
>>> fat and lose it by the end of the journey. The bird can effectively fly
> at
>>> the beginning and end of the mission. In any case, as I have stressed
>>> repeatedly in the literature, it is not possible to restore the mass of
> an
>>> individual specimen better than +/- 20% or more because of problems
>>> with
> restored
>>> volume, SG, and normal changes in an individuals mass. The problem with
> the
>>> Nudds and Dyke was that they overestimated the mass of the
>>> Archaeopteryx
>>> specimen they examined by a factor of about two, Confusicusornis by
> about three.
>>
>> If 20% doesn't matter then I wonder why you bothered adjusting Yalden's
> estimate for the body mass of HMN 1880 by 13% (from 271 to 234g). You also
> spend some time discussing the relative merits of a pectoralis mass
> between 5
> and 15% of body mass.>
>
> Jason is being flippantly unscientific. I did not "adjust" the Yalden
> estimate. When I complete a skeletal restoration I normally do a mass
> estimate
> and the 234 g value is what I happened to came up with for 1880, so I
> published the result. It's the usual technical process.  That the results
> of moi,
> Yalden and Elzanowski are not identical is to be expected especially since
> it
> is not possible to restore body mass closer than ~20%. That they are so
> similar strongly favors their being close to correct. I spend time
> discussing
> the possible pectoralis mass range because that 3 fold difference for the
> specific portion of total mass that actually powers the wings most
> certainly
> does have tremendous importance, duh.
>
>> Moreover, we would both agree that 20% doesn't matter to extant
>> migratory
> birds with highly derived flight apparatus, but modern birds have a lot of
> spare capacity. They can stoop at 200 mph, hover in mid air, and fly
> thousands of miles! In an animal that is barely capable of aerodynamic
> locomotion,
> like any hypothetical ancestor of birds, 20% could be a crucial difference
> between ascending flight and gliding.>
>
> Since the mass of an individual animal can easily vary this much this
> claim
> too is flippant. And to repeat, N&D were off by factors of 2-3, not
> 0.2-0.3.
>
>> I agree that Nudds and Dyke used mass estimates that are too high and
> rachis measurements that were too small, and that their conclusions must
> thus
> be reconsidered. But Zheng et al. found that Nudds and Dyke still
> demonstrated that both birds had weak rachises compared to extant birds of
> the same
> mass. I still think they flew, but this contribution by Nudds and Dyke
> suggests
> that Confuciusornis probably couldn't pull the miraculous maneuvers
> (pouncing on fish and then taking off from the water surface) that
> kingfishers do
> today. >>
>
> How often do I have to repeat this? Can't some of you read? It is
> absolutely impossible to currently restore or compare the feather strength
> and
> therefore flight performance of any Archaeopteryx specimen because in none
> are the
> feather base shafts whose diameter must be measured preserved!!! Give it
> up, the data is simply not available. For the N&D method to be applied to
> the
> urvogel will require the discovery of a new specimen with the primary
> feather bases preserved. Let us hope even as we do not hold our breathes
> (Zheng et
> al say that only 4 of their 536 Confuciusornis specimens have good feather
> bases).
>
> And Zheng et al. did not reanalyze Archaeopteryx.
>
> As for the Zheng et al. reestimate for Confuciusornis feather strength
> they
> are - obviously -- way too pessimistic because they -- hello -- assumed
> that the N&D 3 times too high mass estimate of half a kilogram is correct.
> I
> did not try to come up with a new feather strength estimate in my reply
> because I did not have any Confuciusornis specimens to check out the N&D
> shaft
> diameter measurement which I -- correctly as Z et al proved -- did not
> trust.
> And I am suspicious about the N&D method in any case because it may not
> take
> feather overlap co-bracing into sufficient account. I will not do the
> calculations using my correct mass and Z et al's correct shaft diameters
> because I
> have no plans to further work on the issue at this time there being lots
> of
> other things on my plate, and others will certainly do it and what's wrong
> with that.
>
> GSPaul </HTML>
>


Jason Brougham
Senior Principal Preparator
Department of Exhibition
American Museum of Natural History
81st Street at Central Park West
212 496 3544
jaseb@amnh.org