Re: 11th specimen of Archaeopteryx

[Robert Schenck <schenck.rob@gmail.com>]

Interesting that they're flightless, but they have a flapping ability.
I wonder what the 'deficiencies' in their flight-stroke/anatomy are
that prevent them from making it past 4 meters.

On Tue, Oct 25, 2011 at 12:22 PM, Jason Brougham <jaseb@amnh.org> wrote:
> The literature on the Kagu universally mentions that they glide downhill. It 
> never mentions how far. So I wrote to Yves Letocart, who is the Park 
> Supervisor at the Riviere Bleu national Park in New Caledonia. He started 
> working to conserve the birds in 1980 and is probably single handedly 
> responsible for preventing their extinction. He very graciously answered all 
> of my questions and was very helpful. He is a real hero in my opinion.
>
> He insists that Kagus do not glide. He says that they flap, both when running 
> and in short bursts of flight, such as over streams. He measured it and found 
> that, if the stream is 4 meters wide or less, the birds land on the opposite 
> bank. Any wider and they fall in the water and swim to the opposite bank.
>
> I was researching this because the Kagu has the same mass and wingspan as 
> Microraptor, and if it could glide from the ground that would really be 
> something. But the world's top expert insists it doesn't. There are a few 
> specimens in zoos. I wish we could get a  grad student to go train one and do 
> some basic measurements of its takeoff performance with a force plate and 
> whatnot.
>
> One other note from Letocart - he said Kagus roost in trees at night, more 
> often than on the ground. He said they favor sloping trees, that they walk up 
> the trunk, and that they may leap out if disturbed.
>
>
> On Oct 24, 2011, at 8:18 PM, Tim Williams wrote:
>
>> Michael Habib <MHabib@chatham.edu> wrote:
>>
>> (I've snipped Mike's explanation of feather symmetry vs asymmetry
>> solely for space considerations.  Regrettably, because his summary is
>> the most succinct and comprehensive explanation I've seen to date.)
>>
>>
>>>  In other words, high L:D wing + arboreal adaptations suggests arboreal
>>> living.  High L:D wing + terrestrial adaptations suggests terrestrial 
>>> living.  The high L:D wing is not actually that informative, because it
>>> can apply to either scenario.
>>
>>
>> Definitely.  Further, although the words "arboreal" and "terrestrial"
>> are used to describe the lifestyle of avian ancestors, what this
>> distinction boils down to is the role of gravity in the early
>> evolution of flight.  A terrestrial pro-avian could have spent no time
>> at all in trees, but nevertheless used gliding descents as part of its
>> "terrestrial" behavior.
>>
>> For example, the modern kagu (a secondarily flightless bird) uses its
>> wings for gliding while running over uneven terrain.  The Pouncing
>> Proavis model of Garner et al. (1999) proposed that pro-avians leaped
>> down onto small terrestrial prey from boulders or logs, and used
>> incipient wings to guide the descent.
>>
>> I'm not saying that either of these models are viable hypotheses for
>> incipient flight behavior.  Nevertheless, they underline the fact that
>> "terrestrial" does not automatically require that the pro-avian is
>> always fighting against gravity.  An arboreal ancestry for birds
>> strongly implies a gravity-assisted origin of flight; but a
>> terrestrial ancestry for birds is open to scenarios under which the
>> animal could either be working with or against the force of gravity.
>>
>>
>>> As a closing thought, I am extremely skeptical of WAIR ability in 
>>> Archaeopteryx, for reasons I've posted previously.
>>
>>
>> Yes, me too.  And for reasons I've posted previously (which I suspect
>> agree with the reasons Mike posted previously) the ability to execute
>> WAIR might have been beyond any non-ornithothoracean bird.  It is true
>> that young gallinaceous birds are capable of WAIR, even though their
>> wings are incipient.  But gallinaceous birds (even the young'ns) are
>> endowed with an advanced flight apparatus capable of executing a
>> complete wing stroke; non-avian theropods and basal avians/avialans
>> were not.
>>
>>
>>
>>
>>
>> Cheers
>>
>> Tim
>
> Jason Brougham
> Senior Principal Preparator
> American Museum of Natural History
> jaseb@amnh.org
> (212) 496 3544
>
>
>



-- 
Robert J. Schenck
Kingsborough Community College
Physical Sciences Department
S332 ph# 718-368-5792
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