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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!"



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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