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Re: Brooding over dinos



>What are the average clutch sizes in those birds?  I know ostriches (with
>large wings still) have huge community clutches. Smaller clutches would need
>less wing area to cover chicks.
>
>(Although I don't think wing brooding to be a major factor either
>-- 
> 
>Royan

Rheas may brood up to 30 eggs.  They do indeed cover them with their
feathers -
but they use long, soft contour feathers, not wings, to do so.  There is an
excellent photo showing this for Darwin's Rhea in Vol. 1 of the Handbook of
the
Birds of the World, vol. 1.

This leads me to another problem I have with the brooding hypothesis - there
seems to be something chicken-and-egg about it.  Surely dinosaurs would not
have adopted brooding behaviours they were not physically capable of
performing
efficiently?  Yet you almost need to assume this to speculate that there was a
selective force leading to the evolution of highly complex derived structures
leading from a need to brood more efficiently (as opposed to simply taking
care
of the problem through behavioural shifts).  On the other hand, structures
evolved for other purposes may have permitted an extension of brooding
behaviours - and of course it is possible that once this occurred, some
further
evolution in feather distribution and structure may have evolved in
relation to
brooding (such as brood patches or elongated body feathers capable of
forming a
"skirt" around a large clutch, as in rheas).  I would consider this sort of
thing - that is, evolution of longer, thicker contour feathers - to be much
more likely as a brooding correlate than the evolution of remiges.
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@inforamp.net