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Re: Sci. Am. - present. [long]



J. Wagner writes (in response to a rather vehement post):

>>They cannot explain why Archy's near ancestors (strictly
>>non-arboreal and non-flying or gliding, they say) lengthened the arm while
>>numerous other lines shortened it.
>        Use of the forelimb in prey collection. (or, perhaps, climbing, if
>you believe in "trees down").
>>Even if the animals could climb trees, this ability is not synonymous with
>>arboreal habits or gliding ability.
>        Nor is an ability to run synonymous with strictly non-arboreal
>habits (q.v. kangaroos and goats). Oh, yeah, one thing I'm quite tired of is
>the knee-jerk association of the "arboreal theory of the origin of avian
>flight" and an obligate gliding stage. The two are not necessarily linked.

I have bored this list before with my conviction that bird ancestors could
have been both arboreal and non-gliding - a point that even Pat Shipman's
excellent book does not seem to appreciate this point.  I think this is
because everyone assumes that the purpose of flight is to get from point A
to point B - but many living birds do not use flight in this way.  Instead,
they make short fluttering dashes to reach prey that would otherwise be out
of reach - either a flying insect, or something sitting on a leaf or limb
too light to support the bird's weight - often returning to the same perch.
 A whole range of birds do this - even some fruit-eating birds.  

If proto-wings could have allowed an Archie ancestor to jump a few inches
higher, or stay airborne for a few seconds longer, they might have greatly
increased its ability to take a whole range of foods.  This could happen
either in trees or on the ground, but perhaps is more likely  (as in modern
birds) in trees.  

At least this makes sense to me, but I do not recall if anyone has
suggested this as a route to the origin of bird flight.
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
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