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Re: Again: origin of bird flight
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!"
Timothy J. Williams
Iowa State University
Ames IA 50014
Phone: 515 294 9233
Fax: 515 294 3163
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