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



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