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Re: Life of Birds (vertical running)


David Marjanovic wrote:

What is this stage in your opinion? There are too many interpretations of
*Archaeopteryx* around for me to remember... :-]

I was referring to gross morphology. _Archaeopteryx_ and _Rahonavis_ share more in common than any other bird. (Except perhaps that "Proornis" thing.)

*Rahonavis* seems to have been the better secretary bird. According to a
claw study (an SVP meeting abstract from 1998 I cited in June or July) it
was terrestrial (the claws are straighter than in *Archaeopteryx*), and it
was a better flier, according to its quill knobs and the fact that (despite
the rather long legs!) the ulna is the longest bone in the skeleton,

The secretary bird (_Sagittarius serpentarius_), like most (?all) extant birds of prey, has a pes designed for grasping and holding prey. I don't think the pes of _Rahonavis_ is specialized for this purpose. The slashing claw of _Rahonavis_ may have been useful for *subduing* prey already caught, but (as in _Archaeopteryx_) the pes seems to have had little utility in initially siezing the prey. The flexor tubercles are very weak, and the hallux is too high.


> No, Ken Dial demonstrated it with ground birds (quail or something). [...]
> Also, juvenile ground birds are capable of vertical running in this
> method despite their wings being to stubby to fly... also like theropods.

Cool! So I'll shut up and wait for the paper...
Just one question: How do they get back down again?

This is the easy part. The little chickadee is helped down by a phenomenon known as "gravity".


> Oviraptor and its ilk didn't live around large trees (That I know of), but
> they lived in sand dunes and could have used the WAIR "wing assisted
incline
> running" to go up the dunes. WAIR has many many uses!

Are there such steep dunes?

"Steepness" may not have been the primary problem. I would guess that traction would be the most challenging aspect of negotiating a dune, and the aerodyanamic properties of the forelimb (when beated against the air) may have helped in this respect. I can recall from my childhood days the difficulty of trying to run up sand dunes at the beach without sinking into the sand.



Tim


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