Re: Campbell's even crazier than a MANIAC? (archeopteryx

[Michael Habib <mhabib5@jhmi.edu>]

Augusto Haro wrote:

> Okay, recognizing my ignorance of the morphological adaptations for
> burst flying, I want to ask you these two question, which may help in
> determining the basal state for Neornithes:
>
> -Can be short-range flight and burst-flight equated? All short-range
> flight has to require the power you indicate for burst flight?

Great question.  Technically speaking, you can definitely have a flyer 
with short range and low power - something with small anaerobic 
muscles, for example, would fit.  However, the two traits are more or 
less equated in most modern birds, because crown group birds tend to 
tradeoff along the continuum between stamina and power.  That's a bit 
of a simplification, of course, because the relative muscle mass 
varies, as does planform, etc.  But very few living birds have a 
limited range without also having a power advantage, unless they have 
simply reduced the flight apparatus altogether (which is a whole 
different can of worms).  Early birds could have been limited in range 
without having strong burst performance, for reasons related to basal 
morphology (if, for example, they had a very limited muscle mass, which 
was also largely anaerobic).  However, we can't test that hypothesis 
effectively with a phylogenetic bracket of Neornithines (frustratingly 
enough), because the aforementioned basal morphology is no longer 
represented.  Certainly by the base of Ornithurae, the "typical" flight 
apparatus is rather robust.

> -You said Lithornis did not have adaptations for burst flight. Did you
> find adaptations for sustained flight in this taxon? (more generally,
> are there recognized special adaptations for sustained flight?)

It seems to be adapted to mid-ranged flight, probably in semi-cluttered 
environments.  I know that's vague, but I haven't done a full analysis, 
yet.  Basically, the prelim work yields a sort of average forest-bird 
type fit.  I would expect it to be capable of sustained flight, but not 
in sense of super-extended, incredibly fast flight as seen in 
anseriforms or loons (quite a few ducks cruise above 50 mph - they 
waddle like clowns but fly like rockets).  Lots of living birds fit 
into the general range.  Rollers, large passerines, etc.  I need more 
shoulder data from Lithornis to really be certain, though.

In terms of your more general question, there are some mechanical 
correlates of long-distance, rapid, endurance flight (which is what I 
presume you are referring to).  Strangely, there isn't much literature 
on the osteological correlates, but I'm working on changing that as 
best I can (I'm sure everyone is awaiting the papers with bated 
breath...).

> -You said tinamous have less developed burst-flight characters than
> Galliformes, yet they also fly for a short distance.

True.  There isn't much data on their power output or range, sadly.  
They probably have a bit better endurance, but lower accelerations.  
Problem is that we just don't have the kinematic data - yet.  Part of 
the frustration is that they run and/or retreat to trees when possible, 
so we can't really measure max range.  Galliforms do the same thing, 
but they've been key study species for a range of excellent 
experimental projects, and thus we have the numbers to run with the 
osteology.

> If Lithornis does not fit either the burst- nor sustained- flight
> types, and if short-range flight does not necessarily mean burst-,
> that the short-range was the ancestral character state for Neornithes
> should follow. This does not imply that the Createous birds were
> burst- flyers, perhaps their range of flight was even shorter than in
> tinamous or galliforms.

It's probably more generalist, really (see above).  I wouldn't consider 
a crow to be a short-range flyer, really, for example (despite the fact 
that it has much less range, in terms of continuous flapping, than a 
duck).  The overall muscle fraction for Lithornis seems to have been 
roughly average for a crown-group bird.  Given other morphological 
correlates, it doesn't seem like the anaerobic proportion was 
particularly high, but I suspect it was greater than in highly aerobic 
taxa (like continuous flapping seabirds).  This sort of mid-range is 
typical for moderately maneuvered species in heterogenous habitats.

Cheers,

--Mike


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu