Re: 11th specimen of Archaeopteryx

[Jason Brougham <jaseb@amnh.org>]

I'm not sure but I believe the sternum is extremely small proportional to mass.

On Oct 25, 2011, at 12:43 PM, Robert Schenck wrote:

> 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
> Follow Me on Twitter: @Schenck
> KCC Class Schedule on Google Calendar: http://tinyurl.com/mqwlcy

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544