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

[Mike Habib <biologyinmotion@gmail.com>]

> On Mar 14, 2018, at 1:11 PM, Ruben Safir <ruben@mrbrklyn.com> wrote:
> 
> Sorry - I made an error with the previous email.
> 
> 
>> On Wed, Mar 14, 2018 at 10:03:40AM -0400, Mike Habib wrote:
>> 
>> 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.

Yes, but those that run are aquatic birds that use running launch as a result 
of swimming-related anatomy and the challenges of launching from water. Again, 
see work by Earls, Tobalske, and more...

> 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.  

It would just... land. Without a flight stroke, a leaping launch is just a 
leap. So yes, for phase 2 (climb out), there obviously has to be a flapping 
stroke. But the paper in question found evidence that Archaeopteryx had the 
capacity for a flight stroke (as have other papers - such as the one I 
published with Alex D and Hans L in 2016).

> 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.  

Because the most basal birds were terrestrial, rather than aquatic. Also, 
mapping running launch to phylogenies of living birds always recovers multiple 
independent origins of running launch, all associated with semi-aquatic 
ecologies. Combined with what we know of the physics of takeoff, by far the 
most simple explanation is that running launch is an adaption to water that is 
a derived state.

> 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.

Well, basal birds could already leap, so in a sense itâs just the flight 
stroke evolution thatâs needed.

> 
>> 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 have videos of grebes doing this. So does John Hutchinson. Iâll link one 
later when Iâm not traveling.

> 
> 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.  

Spending time observing birds is great, but again, these are all water birds 
with highly derived anatomy and behaviors associated with their aquatic 
ecology. In terms of the actual aerodynamics, thatâs not something you can 
eyeball.

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

It is not. While some early neornithines might have been shorebirds 
(ecologically), that is probably not the basal state for the clade.

> 
> 
Cheers,

âMike Habib