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>Once flight has evolved, it can be put to all sorts of uses. We really should
>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.

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.
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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