[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: 11th specimen of Archaeopteryx



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