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Re: Origin of feathers



Patrick Norton wrote:
<Webster's dictionary, for example, defines incubation as the use of heat
(usually body heat) to bring about embryonic development in eggs, while
brooding is defined as the care of young birds. Under those definitions, the
use of the term "brooding" to describe the behavior of Oviraptor is
inappropriate, since only eggs were found in the nest.>

Hmmm.  I just pulled my Random House collegeate off the shelf and got, "to sit
upon eggs to be hatched, as a bird."

<I've even searched the literature and talked to a couple ornithologists in a
futile effort to find an example of a modern bird that uses its wing feathers
to incubate eggs. No luck. If Oviraptor really was a "wing incubator", it was
exhibiting an apparently novel behavior.>

I'd like to answer this one yes, no, and maybe.  You didn't look far enough
for wing incubation: the razorbill incubates its one large egg on a cliff
ledge by wrapping one wing around it.  The bobwhite quail lays so many eggs
that it is forced to "clutch" them with its wings in order to keep the
outermost ones from cooling.  The jacaranda, incredibly, picks up its eggs
under its wings and walks across lilly pads with them.  My point here is, wing
feathers and egg incubation go together in a variety of ways, Oviraptor may be
showing us one variation.  Particularly, it is good to bear in mind that most
modern birds have relatively huge breasts.  It is not surprising that they use
these to cover and warm their eggs/young.  Oviraptor was not so well endowed
and seems, as you point out, to be showing a novel behavior.  One might call
it, "how to incubate when you haven't yet evolved a large breast."
   Here it might be worth mentioning that Mark Orsen and I are indeed caught
in a bit of a bind.  Our proposal makes the most sense for theropods
sheltering their chicks, not eggs (because the need for longer feathers is
greater as the brood grows in size - again, check out the duck and falcon
references I mentioned in an earlier posting).  The bind comes from the fact
that Oviraptor is sheltering eggs, not chicks.  So, as you correctly point
out, there is no fossil evidence for chick-sheltering.  However, it is hard to
imagine Oviraptor's behavior changing so much that, once its offspring lost
their shells, it refused to ever cover them again.  Parsimoniously, we should
expect its covering behavior to remain, rather than change, after hatching.
But then again maybe not.
   There - yes, no and maybe.