Re: Again: origin of bird flight

["Tim Williams" <twilliams_alpha@hotmail.com>]

David Marjanovic wrote:


> OK, er... still I think *Archaeopteryx* doesn't look anywhere near a
> climber, so close relatives probably didn't climb much either.

Again: An animal's behavioral repertoire may extend beyond simply what its 
functional anatomy suggests it is *best* at.

Hey, I can climb trees (not very well), and my unguals aren't even sharp and 
tapered.  Give me sharp claws to dig into bark and explain to me how 
advantageous sitting in a tree might be if I feed on small, fast-moving prey 
that might be hard to spot at ground-level.  For a small-ish predator (say 
_Sinornithosaurus_-size) it may be even harder to peak over vegetation to 
spot a lizard in the distance.  But, with smaller body size, it becomes 
easier to climb up a tree (against the force of gravity) and stand on a 
branch (which, hopefully, won't snap under your weight).


> Nesting in trees, BTW, which has often been cited as an advantage of
> arboreality, seems to be a rather recent innovation among Neornithes;
> *Gobipteryx* nests are AFAIK also known to lie on the ground.

A minor but important correction: Nesting in trees might be a recent 
innovation, but simply climbing into trees opportunistically might not be.  
It sure this behavior came a lot earlier, and occurred without the benefit 
of claws specialized for climbing.  After all, organisms have to exhibit a 
behavior before selection can act up on it.  The bird didn't evolve 
scansorial claws and then say to itself "Wow, I can climb trees with these!"


Tim



------------------------------------------------------------



Timothy J. Williams



USDA/ARS Researcher

Agronomy Hall

Iowa State University

Ames IA 50014



Phone: 515 294 9233

Fax:   515 294 3163

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