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Re: BAAD BCF



In a message dated 95-11-30 23:28:03 EST, ornstn@inforamp.net (Ronald
Orenstein) writes:

>>Not as important as escaping predators, because the animals cannot know in
>>advance that food will be found in new regimes. 
>
>Please, George, Lamarck's been dead a long time! :)

Yeah, and that's the kind of reasoning that got him there. (-: :-)

>No animal expanding into a new niche "knows in advance" what it is going to
>find - but a tendency to expand into an area with new food sources and fewer
>competitors is clearly advantageous.

But would this _compel_ the evolution of flight and all its many subtle
anatomical adaptations? I suppose an argument could be built up in which an
arboreal animal improves its leaping ability to a gliding stage, fills the
trees with its successful descendants, whose existence forces improvements to
the gliding stage within one of those descendants, whose descendants fill the
trees with improved gliders, and so forth, until the present stage of
unstable powered flight is attained. (There doesn't seem to be a lot more
room for improvement in the flying abilities of modern avians.) I could get
behind something like this scenario.

>And I think flight evolved
>>first in insectivorous forms, not carnivorous forms, even in the case of
>>avian dinosaurs.
>
>I include insectivory within carnivory - insects being animals, after all.

Well, in that case, we're in agreement (he said as he picked the bugs out of
his teeth...).

> I might just buy the evolution of avian flight as enhancing
>>the pursuit of flying insects--although many insects are caught while
>resting
>>rather than flying--but what other sources of food could be reached by
>flying
>>that couldn't be reached by other, less energetically costly means?
>
>It may be easier to get from one tree canopy to another by flying than by
>any other method, especially if this involves trees on islands, rocky
>outcrops etc.  As I have said gliding animals do this regularly, as do fruit
>bats who certainly don't need flight to "capture" their prey!  Also flight
>may make it easier to feed in one area and roost or breed in another
>(consider the Nutmeg Pigeons, that breed on offshore islets but fly to the
>Australian mainland to feed, at times covering as much as sixty or more
>kilometers a day).

Yeah, I could buy that. Again, I don't know whether it would _compel_ the
evolution of flight, but it would certainly represent an opportunity for a
gliding or flying creature to exploit.