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Re: Arms into wings



In a message dated 3/4/99 2:17:14 PM, Ron Orenstein writes:

<< In fact most modern birds do NOT use their feathers for most brooding,
wing-feathers or otherwise.  Since the major purpose of brooding (certainly
of incubation) is to transfer heat from the parent, insulating structures
such as feathers are actually counterproductive.  Birds generally develop a
bare area, the brood patch, for this purpose.>>

Webster tells us that "brooding" does not equal "incubation." Brooding is
incubation plus additional behaviors. Your first statement is wrong. Most
birds brood in one way or another with wing feathers. Your second statement is
half-true. Heat transfer FROM the chick is just as important, as Oviraptor
probably knew.

<<Wings can be used for shading or to protect young from rain, but I hardly
think this could have driven their evolution.  The best evidence for this,
to me, is the reduction of wing feathers in flightless birds.  If brooding
were a major factor in selecting for well-developed wing-feathers  I would
expect these to be retained in flightless birds, which brood their young in
the same manner as flying birds.  Why, for example, would ostriches have
large remiges, but not emus or rheas?>>

Regardless of all the alternatives that may have evolved, there is no reason
why a "flight" feathered theropod could not have evolved under brooding
pressure. It isn't so much: "can we think of an alternative," as: "could this
have happened." Perhaps the "flight" type feather was the first form of
feather, as some have suggested. Then, clearly, the simplest brooding solution
is to use what's available.

And regarding the roadrunner as a transitional cursor/flyer model, DinoGeorge
wrote:

<<Here's where your model is moot: I assert that the roadrunner is even better
as a model of a bird in the process of >losing< (not acquiring) its flying
ability--a stage in the evolution of a secondarily flightless, ground-dwelling
cursorial form from a flying ancestor.>>

But George, the roadrunner IS NOT "a stage in the evolution of a secondarily
flightless, ground-dwelling cursorial form from a flying ancestor." It just
IS. And what it is, is a running hunter that occasionally leaps up and delays
its return to earth by flapping. It is a fine model for both scenarios.
Therefore, my scenario doesn't lack a modern example. Neither does yours.

Tom Hopp