Re: [dinosaur] Archaeopteryx had active flapping flight ability based on wing bone geometry (free pdf)

[Ruben Safir <ruben@mrbrklyn.com>]

On Wed, Mar 14, 2018 at 10:03:40AM -0400, Mike Habib wrote:
> Running launch is an adaptation to water takeoff; it is a specialist form of 
> takeoff and is not typical of most birds. 
> 
> In most cases, terrestrial launch is initiated via leaping (ie it is hind 
> limb driven). The wings engage in a downstroke *after* toe off, exactly as 
> Tim noted. In fact, leaping launch powered by the walking limbs is typical 
> for both powered and unpowered flyers (see work by Earls, Tobalske, 
> Nachtigall, etc). This is why launch is can be looked at as a two-phase 
> process: a walking limb driven phase I (launch proper) and a wing driven 
> phase II (climb out).
> 

That is with well evolved modern birds, and not all of them at all.
Chickens will also do a running take off.  Anyway you slice it, unless
you have sufficient wing power then launching by leaping has zero value.
A bird will land on its face every time.  Geese and grouse will also
run with wings spread out developing lift.

Your saying, I assume with reason, that the water borne method is later
an adaptation.  I'd like to see the proof of that and how you know it is
not actually an ancestral trait.  Regardless.  It is impossible to image
that the birds would develop the leaping launch that is so prevalent
without the strong upward flight stroke and the two can not be separated.

> The role of the wings in water launch is not well understood. Water birds can 
> run on the surface without using the wings, 

No.  Please show me a species that can get speed for flight by running
on water without the help of its wings.  I'd like to see the species
that can do this, but this is in no way what most seabirds or waterfowl 
are capable of.

> so the build up of speed across the surface seems not to be wing dependent. 
> It is likely that the wings are used either for stability or simply to build 
> vorticity prior to launch (ie to counter the Wagner Effect), since running 
> launch accelerations are lower than leaping launch accelerations.
> 

If you say birds can walk on water without wing assist, I'll take your
word for it although I fail to see how that is relevant. I've never seen
Swans do this and seriously doubt they can.  I've been observing swans
daily from the docks of Sheepshead bay, carefully studying them, and
Cormorants, Ducks, and Canadian Geese.  Swans could never get lift
without a running start.  Some ducks will, on rare occasion if startled.
Swans can not.  They run while flapping well over 3 city blocks before
they get enough speed to be airborne low to the water and then gradually
gain altitude.

In the end analysis, FWIW, birds will do whatever they can do.  They
have no set mechanism for anything, either running, flying or launching.
My African Grey Parrot will hang upside down from the perch and open his
wings wide, and just start screaming and let go, dropping in a control
fall while turning midair rightside up, claws down and attack my
cat...for the fun of it.  And end up swooping up to the fridge.

Anyway, as I said, the leap your familiar with would be impossible
without the upstroke.  They had to co-evolve.  When you cut the flight
feathers of a parrot, this becomes all too clear when the bird drops to
the floor accidentally, not realizing it has been restricted.  However,
if they do jump from height, and catch wind, they can get airborne sometimes 
with much less control.

The other wrinkle in this conversation is that, if I recall previous
discussions, modern birds evolved from waterfowl.  Is that still the
working hypothesis?


> Cheers,
> 
> âMike Habib
> 
> Sent from my Cybernetic Symbiote
> 
> > On Mar 14, 2018, at 3:39 AM, Ruben Safir <ruben@mrbrklyn.com> wrote:
> > 
> >> On 03/13/2018 11:29 PM, Tim Williams wrote:
> >> Vertical take-offs are initiated by the hindlimbs in extant
> >> birds (Earls 2000 JEB 203: 725-739), and it's likely that
> >> _Archaeopteryx_ was capable of the same (leaping into the air, with no
> >> need for a running take-off; Dececchi et al. 2016 DOI
> >> 10.7717/peerj.2159). The wings are deployed for the climb-out phase of
> >> the launch, and a modern avian flight stroke is not essential for this
> >> - just large wings capable of thrust generation.
> > 
> > Without the lift from the wing stroke the bird just lands on its face
> > and the separation of these two aspects of launch that you make here is
> > illogical.  Furthermore, despite what Earls says, I recommend you walk
> > out to Sheepshead Bay in Brooklyn and watch how Swans and Ducks actually
> > get into the air.  Swans are not leaping into the air and then taking
> > off on winged power.  They 100% depend on building air speed with a
> > combination of flight stroke and running on the water.  Without a
> > sternum to anchor chest muscles, that is going to be more true, not
> > less.  Flight stroke IS 100% essential.  Maybe there is someones next
> > research paper.
> > 
> > 

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