Re: feathers for brooding

[Jeff Hecht <jhecht@world.std.com>]

Betty Cunningham wrote:
>this isn't a new idea.  It was proposed on the Dinosaur list
>(I think GSP Dec 95 beat everyone else out on it)
>http://www.cmnh.org/fun/dinosaur-archive/1995Dec/0852.html
>
>"It is interesting that the body and arms did not entirely cover the
>eggs.
>This hints that insulation was present to cover the eggs for both heat
>retention, and shading, as in birds."
>
This isn't exactly the same thing. Thomas Hopp showed how primary and
secondary wing feathers would neatly cover the exposed areas of the nest,
if Oviraptor had them. He also suggested that brooding could have driven
the evolution of long feathers on the arms. A dinosaur with small
insulating feathers would not have gotten any direct evolutionary advantage
from longer feathers on the arm for other purposes. However, by evolving
longer brooding feathers, the animal would have been able to brood a larger
clutch of eggs, and protect more young once they had hatched. Note this is
a marginal advantage -- the longer the feathers, the more nestlings can be
shielded. Then once the feathers had grown long enough, they could have
helped the animal get off the ground as a bird -- perhaps first by leaping.

Hopp showed photos of several birds in similar postures covering eggs or
taking youngs "under their wings" -- including ostriches, ducks, and
falcons. Larry Martin did note that the Oviraptor eggs seemed to be buried
in the sand, but the animal could have taken an instinctive protective
position to cover the eggs in a downpour, and been caught surprised by a
wet-sand avalanche (which I believe is now thought responsible for the
deposits).

What's new - at least to me -- is the explanation of the evolutionary
transition from insulating feathers to flight feathers, which otherwise
required Ostrom's "impossible animal" that flapped its wings while chasing
insects. There clearly are questions to be answered, but it's a credible
hypothesis.

By the way, my apologies for referring you to articles that New Scientist
_didn't_ post on the web site. I had thought the articles would be posted.
-- Jeff Hecht

Jeff Hecht     Boston Correspondent    New Scientist magazine
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