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In a message dated 95-11-30 23:31:51 EST, ornstn@inforamp.net (Ronald
Orenstein) writes:

>>Once flight has evolved, it can be put to all sorts of uses. We really
>>separate proximate causes from opportunistic functions. (Or whatever.)
>Fair enough, but how?  Assigning as proximate causes those that fit one's
>pet thories and assigning other uses to the "opportunistic" category doesn't
>seem like the way to proceed.

That's the _only_ way to proceed!

>After all, if flight evolved AFTER protobirds became arboreal, presumably
>the main issue of avoidance of ground predators had already been dealt with
>- so flight would add little or no advantage if that were the driving
>concern.  The question "why should an animal in already in a tree need to
>fly if its predators are on the ground" seems most easily answered by saying
>"to get to another tree".  And why do that?  Foraging opportunities seem at
>least a possible explanation.

But how about the arboreal predators--the ones that can chase you up a tree
and then follow you around from branch to branch (like felids, e.g.). Here,
by the way, being lighweight has an advantage: you can sometimes escape to
branches too small to hold your pursuer.